JEWISH SOURCES ON GUN CONTROL AND GUN RIGHTS Based on lectures by R' Yuter, R’ Flug, R’ Pruzansky, R’ Brody, R' Bleich and R’ Taubes
(א) וַיְדַבֵּ֨ר ה' אֶל־מֹשֶׁ֛ה בְּמִדְבַּ֥ר סִינַ֖י בְּאֹ֣הֶל מוֹעֵ֑ד בְּאֶחָד֩ לַחֹ֨דֶשׁ הַשֵּׁנִ֜י בַּשָּׁנָ֣ה הַשֵּׁנִ֗ית לְצֵאתָ֛ם מֵאֶ֥רֶץ מִצְרַ֖יִם לֵאמֹֽר׃ (ב) שְׂא֗וּ אֶת־רֹאשׁ֙ כָּל־עֲדַ֣ת בְּנֵֽי־יִשְׂרָאֵ֔ל לְמִשְׁפְּחֹתָ֖ם לְבֵ֣ית אֲבֹתָ֑ם בְּמִסְפַּ֣ר שֵׁמ֔וֹת כָּל־זָכָ֖ר לְגֻלְגְּלֹתָֽם׃ (ג) מִבֶּ֨ן עֶשְׂרִ֤ים שָׁנָה֙ וָמַ֔עְלָה כָּל־יֹצֵ֥א צָבָ֖א בְּיִשְׂרָאֵ֑ל תִּפְקְד֥וּ אֹתָ֛ם לְצִבְאֹתָ֖ם אַתָּ֥ה וְאַהֲרֹֽן׃
(1) On the first day of the second month, in the second year following the exodus from the land of Egypt, the LORD spoke to Moses in the wilderness of Sinai, in the Tent of Meeting, saying: (2) Take a census of the whole Israelite community by the clans of its ancestral houses, listing the names, every male, head by head. (3) You and Aaron shall record them by their groups, from the age of twenty years up, all those in Israel who are able to bear arms.
(כא) וַיָּ֤קָם בִּלְעָם֙ בַּבֹּ֔קֶר וַֽיַּחֲבֹ֖שׁ אֶת־אֲתֹנ֑וֹ וַיֵּ֖לֶךְ עִם־שָׂרֵ֥י מוֹאָֽב׃ (כב) וַיִּֽחַר־אַ֣ף אֱלֹקִים֮ כִּֽי־הוֹלֵ֣ךְ הוּא֒ וַיִּתְיַצֵּ֞ב מַלְאַ֧ךְ ה' בַּדֶּ֖רֶךְ לְשָׂטָ֣ן ל֑וֹ וְהוּא֙ רֹכֵ֣ב עַל־אֲתֹנ֔וֹ וּשְׁנֵ֥י נְעָרָ֖יו עִמּֽוֹ׃ (כג) וַתֵּ֣רֶא הָאָתוֹן֩ אֶת־מַלְאַ֨ךְ ה' נִצָּ֣ב בַּדֶּ֗רֶךְ וְחַרְבּ֤וֹ שְׁלוּפָה֙ בְּיָד֔וֹ וַתֵּ֤ט הָֽאָתוֹן֙ מִן־הַדֶּ֔רֶךְ וַתֵּ֖לֶךְ בַּשָּׂדֶ֑ה וַיַּ֤ךְ בִּלְעָם֙ אֶת־הָ֣אָת֔וֹן לְהַטֹּתָ֖הּ הַדָּֽרֶךְ׃
(21) When he arose in the morning, Balaam saddled his ass and departed with the Moabite dignitaries. (22) But God was incensed at his going; so an angel of the LORD placed himself in his way as an adversary. He was riding on his she-ass, with his two servants alongside, (23) when the ass caught sight of the angel of the LORD standing in the way, with his drawn sword in his hand. The ass swerved from the road and went into the fields; and Balaam beat the ass to turn her back onto the road.
(טז) וַיִּשָּׂ֨א דָוִ֜יד אֶת־עֵינָ֗יו וַיַּ֞רְא אֶת־מַלְאַ֤ךְ ה' עֹמֵ֗ד בֵּ֤ין הָאָ֙רֶץ֙ וּבֵ֣ין הַשָּׁמַ֔יִם וְחַרְבּ֤וֹ שְׁלוּפָה֙ בְּיָד֔וֹ נְטוּיָ֖ה עַל־יְרוּשָׁלִָ֑ם וַיִּפֹּ֨ל דָּוִ֧יד וְהַזְּקֵנִ֛ים מְכֻסִּ֥ים בַּשַּׂקִּ֖ים עַל־פְּנֵיהֶֽם׃
(16) David looked up and saw the angel of the LORD standing between heaven and earth, with a drawn sword in his hand directed against Jerusalem. David and the elders, covered in sackcloth, threw themselves on their faces.
(ט) וַיִּתֵּ֥ן יוֹאָ֛ב אֶת־מִסְפַּ֥ר מִפְקַד־הָעָ֖ם אֶל־הַמֶּ֑לֶךְ וַתְּהִ֣י יִשְׂרָאֵ֡ל שְׁמֹנֶה֩ מֵא֨וֹת אֶ֤לֶף אִֽישׁ־חַ֙יִל֙ שֹׁ֣לֵֽף חֶ֔רֶב וְאִ֣ישׁ יְהוּדָ֔ה חֲמֵשׁ־מֵא֥וֹת אֶ֖לֶף אִֽישׁ׃
(9) Joab reported to the king the number of the people that had been recorded: in Israel there were 800,000 soldiers ready to draw the sword, and the men of Judah numbered 500,000.
(יט) וְחָרָשׁ֙ לֹ֣א יִמָּצֵ֔א בְּכֹ֖ל אֶ֣רֶץ יִשְׂרָאֵ֑ל כִּֽי־אמר [אָמְר֣וּ] פְלִשְׁתִּ֔ים פֶּ֚ן יַעֲשׂ֣וּ הָעִבְרִ֔ים חֶ֖רֶב א֥וֹ חֲנִֽית׃
(19) No smith was to be found in all the land of Israel, for the Philistines were afraid that the Hebrews would make swords or spears.
(א) אִם־בַּמַּחְתֶּ֛רֶת יִמָּצֵ֥א הַגַּנָּ֖ב וְהֻכָּ֣ה וָמֵ֑ת אֵ֥ין ל֖וֹ דָּמִֽים׃ (ב) אִם־זָרְחָ֥ה הַשֶּׁ֛מֶשׁ עָלָ֖יו דָּמִ֣ים ל֑וֹ שַׁלֵּ֣ם יְשַׁלֵּ֔ם אִם־אֵ֣ין ל֔וֹ וְנִמְכַּ֖ר בִּגְנֵבָתֽוֹ׃ (ג) אִֽם־הִמָּצֵא֩ תִמָּצֵ֨א בְיָד֜וֹ הַגְּנֵבָ֗ה מִשּׁ֧וֹר עַד־חֲמ֛וֹר עַד־שֶׂ֖ה חַיִּ֑ים שְׁנַ֖יִם יְשַׁלֵּֽם׃ (ס)
(1) If the thief is seized while tunneling, and he is beaten to death, there is no bloodguilt in his case. (2) If the sun has risen on him, there is bloodguilt in that case.—He must make restitution; if he lacks the means, he shall be sold for his theft. (3) But if what he stole—whether ox or ass or sheep—is found alive in his possession, he shall pay double.

(ו) הַבָּא בַמַּחְתֶּרֶת נִדּוֹן עַל שֵׁם סוֹפוֹ. הָיָה בָא בַמַּחְתֶּרֶת וְשָׁבַר אֶת הֶחָבִית, אִם יֶשׁ לוֹ דָמִים, חַיָּב. אִם אֵין לוֹ דָמִים, פָּטוּר:

(6) [The thief] who burrows his way in [to someone’s home] is judged on account of his outcome. If he burrowed his way in and broke a jug, should there be blood-guiltiness for him, he must pay [for the jug], but if there is no blood-guiltiness for him, he is not liable.

גמ׳ אמר רבא מאי טעמא דמחתרת חזקה אין אדם מעמיד עצמו על ממונו והאי מימר אמר אי אזילנא קאי לאפאי ולא שביק לי ואי קאי לאפאי קטילנא ליה והתורה אמרה אם בא להורגך השכם להורגו
GEMARA: Rava says: What is the reason for this halakha concerning a burglar who breaks into a house? He explains: There is a presumption that a person does not restrain himself when faced with losing his money, and therefore this burglar must have said to himself: If I go in and the owner sees me, he will rise against me and not allow me to steal from him, and if he rises against me, I will kill him. And the Torah stated a principle: If someone comes to kill you, rise and kill him first.
תנו רבנן (שמות כב, א) והוכה בכל אדם ומת בכל מיתה שאתה יכול להמיתו בשלמא והוכה בכל אדם איצטריך סד"א בעל הבית הוא דקים (להו) דאין אדם מעמיד עצמו על ממונו אבל אחר לא
§ Concerning the verse that states: “If a burglar is found breaking in, and is smitten and dies, there shall not be blood shed on his account” (Exodus 22:1), the Sages taught a baraita: “And is smitten,” by any person who strikes him; “and dies,” by any means of death by which you can put him to death. The Gemara clarifies this baraita: Granted, with regard to the words “and is smitten,” it was necessary to say that he may be struck by any person, as it might enter your mind to say that it is only the owner of the house whom the burglar is certain will resist him, because there is a presumption that a person does not restrain himself when faced with losing his money, and therefore it is only the homeowner’s life that is in danger from the burglar. But as for another person, the burglar is not sure that he will try to stop him, and therefore that other person may not kill him, since the burglar did not come with the intention of killing him.
גמ׳ ת"ר מניין לרודף אחר חבירו להרגו שניתן להצילו בנפשו ת"ל (ויקרא יט, טז) לא תעמוד על דם רעך והא להכי הוא דאתא האי מיבעי ליה לכדתניא מניין לרואה את חבירו שהוא טובע בנהר או חיה גוררתו או לסטין באין עליו שהוא חייב להצילו ת"ל לא תעמוד על דם רעך אין ה"נ
GEMARA: The Sages taught in a baraita: From where is it derived that with regard to one who pursues another in order to kill him, the pursued party may be saved at the cost of the pursuer’s life? The verse states: “You shall not stand idly by the blood of another” (Leviticus 19:16); rather, you must save him from death. The Gemara asks: But does this verse really come to teach us this? This verse is required for that which is taught in a baraita: From where is it derived that one who sees another drowning in a river, or being dragged away by a wild animal, or being attacked by bandits [listin], is obligated to save him? The Torah states: “You shall not stand idly by the blood of another.” The Gemara answers: Yes, it is indeed so that this verse relates to the obligation to save one whose life is in danger.
רבי אליעזר אומר תכשיטין הן לו: תניא אמרו לו לרבי אליעזר וכי מאחר דתכשיטין הן לו מפני מה הן בטלין לימות המשיח אמר להן לפי שאינן צריכין שנאמר לא ישא גוי אל גוי חרב ותהוי לנוי בעלמא אמר אביי מידי דהוה אשרגא בטיהרא ופליגא דשמואל דאמר שמואל אין בין העולם הזה לימות המשיח אלא שיעבוד גליות בלבד שנאמר כי לא יחדל אביון מקרב הארץ
We learned in the mishna that Rabbi Eliezer says: These weapons are ornaments for him. It was taught in a baraita that elaborates on this subject: The Rabbis said to Rabbi Eliezer: And since, in your opinion, they are ornaments for him, why are they to be eliminated in the messianic era? He said to them: They will not be needed anymore, as it is stated: “Nation will not raise sword against nation” (Isaiah 2:4). The Gemara asks: And let the weapons be merely for ornamental purposes, even though they will not be needed for war. Abaye said: It is just as in the case of a candle in the afternoon. Since its light is not needed, it serves no ornamental purpose. Weapons, too; when not needed for war, they serve no ornamental purpose either. And this baraita disagrees with the opinion of Shmuel, as Shmuel said: The only difference between this world and the messianic era is subjugation of the exiles to other kingdoms, from which the Jewish people will be released. However, in other respects, the world will remain as it is, as it is written: “Because the poor will not cease from within the land” (Deuteronomy 15:11). Society will not change, and wars will continue to be waged.
ואין מוכרין בהן לא כלי זיין ולא כלי מצודה דברי רבי נחמיה וחכמים מתירין ושוין שאין פורסין בתוכן מצודות ואין מפשילין לתוכן חבלים כדי שלא תהא רגל גואל הדם מצויה שם

The baraita continues: And one may not sell weapons or hunting tools in the cities of refuge, to prevent the blood redeemer from gaining access to means that he could exploit to kill the unintentional murderer who fled to the city of refuge; this is the statement of Rabbi Neḥemya. And the Rabbis permit selling weapons and hunting tools. And Rabbi Neḥemya and the Rabbis agree that one may not spread nets in the cities of refuge, nor may they braid [mafshilin] ropes in those cities, so that the foot of the blood redeemer will not be found there. If the blood redeemer were to enter the city of refuge to purchase nets or ropes, he is apt to encounter the murderer and kill him.

R. Isaac asked: What is the Scriptural authority [for all these provisions]? — The verse, "and that fleeing unto one of these cities he might live" [Devarim 4:42] which means — provide him with whatever he needs so that he may live.

לא יגדל אדם את הכלב אא"כ קשור בשלשלאות כו': תנו רבנן לא יגדל אדם את הכלב אלא אם כן קשור בשלשלת אבל מגדל הוא בעיר הסמוכה לספר וקושרו ביום ומתירו בלילה
§ The mishna teaches: A person may not raise a dog unless it is tied with chains. The Sages taught in a baraita: A person may not raise a dog unless it is tied with a chain. But he may raise a dog in a city that is close to the border of the country, and in that case he should tie it during the day but may release it at night.
אָדָם מוּעָד לְעוֹלָם, בֵּין שׁוֹגֵג, בֵּין מֵזִיד, בֵּין עֵר, בֵּין יָשֵׁן. סִמֵּא אֶת עֵין חֲבֵרוֹ וְשִׁבֵּר אֶת הַכֵּלִים, מְשַׁלֵּם נֶזֶק שָׁלֵם:
Human beings are always an attested danger, whether the damage is caused inadvertently or deliberately, whether the person who caused the damage is awake or asleep. If a man blinded his fellow’s eye or broke his utensils he must pay full damages.
(יט) וַיִּֽקַּֽח־ל֥וֹ לֶ֖מֶךְ שְׁתֵּ֣י נָשִׁ֑ים שֵׁ֤ם הָֽאַחַת֙ עָדָ֔ה וְשֵׁ֥ם הַשֵּׁנִ֖ית צִלָּֽה׃ (כ) וַתֵּ֥לֶד עָדָ֖ה אֶת־יָבָ֑ל ה֣וּא הָיָ֔ה אֲבִ֕י יֹשֵׁ֥ב אֹ֖הֶל וּמִקְנֶֽה׃ (כא) וְשֵׁ֥ם אָחִ֖יו יוּבָ֑ל ה֣וּא הָיָ֔ה אֲבִ֕י כָּל־תֹּפֵ֥שׂ כִּנּ֖וֹר וְעוּגָֽב׃ (כב) וְצִלָּ֣ה גַם־הִ֗וא יָֽלְדָה֙ אֶת־תּ֣וּבַל קַ֔יִן לֹטֵ֕שׁ כָּל־חֹרֵ֥שׁ נְחֹ֖שֶׁת וּבַרְזֶ֑ל וַֽאֲח֥וֹת תּֽוּבַל־קַ֖יִן נַֽעֲמָֽה׃ (כג) וַיֹּ֨אמֶר לֶ֜מֶךְ לְנָשָׁ֗יו עָדָ֤ה וְצִלָּה֙ שְׁמַ֣עַן קוֹלִ֔י נְשֵׁ֣י לֶ֔מֶךְ הַאְזֵ֖נָּה אִמְרָתִ֑י כִּ֣י אִ֤ישׁ הָרַ֙גְתִּי֙ לְפִצְעִ֔י וְיֶ֖לֶד לְחַבֻּרָתִֽי׃ (כד) כִּ֥י שִׁבְעָתַ֖יִם יֻקַּם־קָ֑יִן וְלֶ֖מֶךְ שִׁבְעִ֥ים וְשִׁבְעָֽה׃ (כה) וַיֵּ֨דַע אָדָ֥ם עוֹד֙ אֶת־אִשְׁתּ֔וֹ וַתֵּ֣לֶד בֵּ֔ן וַתִּקְרָ֥א אֶת־שְׁמ֖וֹ שֵׁ֑ת כִּ֣י שָֽׁת־לִ֤י אֱלֹקִים֙ זֶ֣רַע אַחֵ֔ר תַּ֣חַת הֶ֔בֶל כִּ֥י הֲרָג֖וֹ קָֽיִן׃ (כו) וּלְשֵׁ֤ת גַּם־הוּא֙ יֻלַּד־בֵּ֔ן וַיִּקְרָ֥א אֶת־שְׁמ֖וֹ אֱנ֑וֹשׁ אָ֣ז הוּחַ֔ל לִקְרֹ֖א בְּשֵׁ֥ם ה'׃ (פ)
(19) Lamech took to himself two wives: the name of the one was Adah, and the name of the other was Zillah. (20) Adah bore Jabal; he was the ancestor of those who dwell in tents and amidst herds. (21) And the name of his brother was Jubal; he was the ancestor of all who play the lyre and the pipe. (22) As for Zillah, she bore Tubal-cain, who forged all implements of copper and iron. And the sister of Tubal-cain was Naamah. (23) And Lamech said to his wives, “Adah and Zillah, hear my voice; O wives of Lamech, give ear to my speech. I have slain a man for wounding me, And a lad for bruising me. (24) If Cain is avenged sevenfold, Then Lamech seventy-sevenfold.” (25) Adam knew his wife again, and she bore a son and named him Seth, meaning, “God has provided me with another offspring in place of Abel,” for Cain had killed him. (26) And to Seth, in turn, a son was born, and he named him Enosh. It was then that men began to invoke the LORD by name.

ויאמר למך לנשיו... אבל הנראה בעיני כי היה למך איש חכם מאד בכל מלאכת מחשבת ולמד לבנו הבכור ענין המרעה כפי טבעי הבהמות ולמד את השני חכמת הנגון ולמד את השלישי ללטוש ולעשות חרבות ורמחים וחניתות וכל כלי המלחמה והיו נשיו מתפחדות שלא יענש כי הביא החרב והרציחה בעולם והנה הוא תופש מעשה אבותיו בידו כי הוא בן המרצח הראשון וברא משחית לחבל והוא אמר להן אני לא הרגתי איש לפצעים ולא ילד לחבורות כאשר עשה קין ולא יענישני השם אבל ישמרני מן ההריגה יותר ממנו והזכיר כן לומר כי לא בחרב וחנית יכול אדם להרוג בפצעים וחבורות שימית במיתה רעה יותר מן החרב ואין החרב גורם הרציחה ואין על העושו חטא

The wives of Lamech feared that he [Lamech] may be punished, for he brought sword and murder into the world, for he had continued in the ways of his fathers, the first smiths… And he said the to them 'I have not killed a man for my bruise, or a youth for my injury as Cain did. Thus, Hashem will not punish me but rather protect me from being killed far more than him. And he reminded them that it is not the sword or spear which kills a man but the wound which is inflicted upon him… and it is not the sword that causes murder, and thus on its creator there is no sin.

(ד) לֹא יֵצֵא הָאִישׁ לֹא בְסַיִף, וְלֹא בְקֶשֶׁת, וְלֹא בִתְרִיס, וְלֹא בְאַלָּה, וְלֹא בְרֹמַח. וְאִם יָצָא, חַיָּב חַטָּאת. רַבִּי אֱלִיעֶזֶר אוֹמֵר, תַּכְשִׁיטִין הֵן לוֹ. וַחֲכָמִים אוֹמְרִים, אֵינָן אֶלָּא לִגְנַאי, שֶׁנֶּאֱמַר (ישעיה ב) וְכִתְּתוּ חַרְבוֹתָם לְאִתִּים וַחֲנִיתוֹתֵיהֶם לְמַזְמֵרוֹת, לֹא יִשָּׂא גּוֹי אֶל גּוֹי חֶרֶב וְלֹא יִלְמְדוּ עוֹד מִלְחָמָה. בִּירִית, טְהוֹרָה, וְיוֹצְאִין בָּהּ בְּשַׁבָּת. כְּבָלִים, טְמֵאִין, וְאֵין יוֹצְאִין בָּהֶם בְּשַׁבָּת:

(4) A man may not go out with a sword, bow, shield, club, or spear, and if he does go out, he incurs a sin-offering. Rabbi Eliezer says: they are ornaments for him. But the sages say, they are nothing but a disgrace, as it is said, “And they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more” (Isaiah 2:4). A garter is clean, and they go out [wearing] it on Shabbat. Knee-bands are unclean, and they may not go out with them on Shabbat.

(ד) וְשָׁפַט֙ בֵּ֣ין הַגּוֹיִ֔ם וְהוֹכִ֖יחַ לְעַמִּ֣ים רַבִּ֑ים וְכִתְּת֨וּ חַרְבוֹתָ֜ם לְאִתִּ֗ים וַחֲנִיתֽוֹתֵיהֶם֙ לְמַזְמֵר֔וֹת לֹא־יִשָּׂ֨א ג֤וֹי אֶל־גּוֹי֙ חֶ֔רֶב וְלֹא־יִלְמְד֥וּ ע֖וֹד מִלְחָמָֽה׃ (פ)
(4) Thus He will judge among the nations And arbitrate for the many peoples, And they shall beat their swords into plowshares And their spears into pruning hooks: Nation shall not take up Sword against nation; They shall never again know war.
(כב) וְאִם־מִזְבַּ֤ח אֲבָנִים֙ תַּֽעֲשֶׂה־לִּ֔י לֹֽא־תִבְנֶ֥ה אֶתְהֶ֖ן גָּזִ֑ית כִּ֧י חַרְבְּךָ֛ הֵנַ֥פְתָּ עָלֶ֖יהָ וַתְּחַֽלְלֶֽהָ׃

(22) And if you make for Me an altar of stones, do not build it of hewn stones; for by wielding your sword upon them you have profaned them.

ותחללה. הָא לָמַדְתָּ שֶׁאִם הֵנַפְתָּ עָלֶיהָ בַּרְזֶל חִלַּלְתָּ, שֶׁהַמִּזְבֵּחַ נִבְרָא לְהַאֲרִיךְ יָמָיו שֶׁל אָדָם וְהַבַּרְזֶל נִבְרָא לְקַצֵּר יָמָיו שֶׁל אָדָם, אֵין זֶה בַּדִּין שֶׁיּוּנַף הַמְקַצֵּר עַל הַמַּאֲרִיךְ (מכילתא). וְעוֹד שֶׁהַמִּזְבֵּחַ מֵטִיל שָׁלוֹם בֵּין יִשְׂרָאֵל לַאֲבִיהֶם שֶׁבַּשָּׁמַיִם, לְפִיכָךְ לֹא יָבֹא עָלָיו כּוֹרֵת וּמְחַבֵּל; וַהֲרֵי דְּבָרִים קַל וָחֹמֶר, וּמָה אֲבָנִים שֶׁאֵינָן רוֹאוֹת וְלֹא שׁוֹמְעוֹת וְלֹא מְדַבְּרוֹת, עַל יְדֵי שֶׁמְּטִילוֹת שָׁלוֹם אָמְרָה תּוֹרָה וְלֹא תָנִיף עֲלֵיהֶם בַּרְזֶל, הַמֵּטִיל שָׁלוֹם בֵּין אִישׁ לְאִשְׁתּוֹ, בֵּין מִשְׁפָּחָה לְמִשְׁפָּחָה, בֵּין אָדָם לַחֲבֵרוֹ, עַל אַחַת כַּמָּה וְכַמָּה שֶׁלֹּא תְבוֹאֵהוּ פֻּרְעָנוּת (שם):

ותחללה THEN THOU HAST PROFANED IT — Thus you may learn that if thou liftest up thy iron tool above it thou profanest it. The reason of this it, because the altar is created (its purpose is) to lengthen man’s days and iron has been created (one of its purposes is) to shorten man’s days, it is not right that an object which shortens man’s life should be lifted up above that which lengthens it (Mekhilta, Middoth 3:4).

ותחללה. הָא לָמַדְתָּ שֶׁאִם הֵנַפְתָּ עָלֶיהָ בַּרְזֶל חִלַּלְתָּ, שֶׁהַמִּזְבֵּחַ נִבְרָא לְהַאֲרִיךְ יָמָיו שֶׁל אָדָם וְהַבַּרְזֶל נִבְרָא לְקַצֵּר יָמָיו שֶׁל אָדָם, אֵין זֶה בַּדִּין שֶׁיּוּנַף הַמְקַצֵּר עַל הַמַּאֲרִיךְ (מכילתא). וְעוֹד שֶׁהַמִּזְבֵּחַ מֵטִיל שָׁלוֹם בֵּין יִשְׂרָאֵל לַאֲבִיהֶם שֶׁבַּשָּׁמַיִם, לְפִיכָךְ לֹא יָבֹא עָלָיו כּוֹרֵת וּמְחַבֵּל; וַהֲרֵי דְּבָרִים קַל וָחֹמֶר, וּמָה אֲבָנִים שֶׁאֵינָן רוֹאוֹת וְלֹא שׁוֹמְעוֹת וְלֹא מְדַבְּרוֹת, עַל יְדֵי שֶׁמְּטִילוֹת שָׁלוֹם אָמְרָה תּוֹרָה וְלֹא תָנִיף עֲלֵיהֶם בַּרְזֶל, הַמֵּטִיל שָׁלוֹם בֵּין אִישׁ לְאִשְׁתּוֹ, בֵּין מִשְׁפָּחָה לְמִשְׁפָּחָה, בֵּין אָדָם לַחֲבֵרוֹ, עַל אַחַת כַּמָּה וְכַמָּה שֶׁלֹּא תְבוֹאֵהוּ פֻּרְעָנוּת (שם):
ותחללה THEN THOU HAST PROFANED IT — Thus you may learn that if thou liftest up thy iron tool above it thou profanest it. The reason of this it, because the altar is created (its purpose is) to lengthen man’s days and iron has been created (one of its purposes is) to shorten man’s days, it is not right that an object which shortens man’s life should be lifted up above that which lengthens it (Mekhilta, Middoth 3:4). And a further reason it: because the altar makes peace between Israel and their Father in Heaven, and therefore there should not come upon it anything that cuts and destroys. Now, the following statement follows logically, à fortiori: How is it in the case of stones which cannot see nor hear nor speak? Because that they promote peace Scripture ordains, “Thou shalt not lift up against them any iron tool!” Then in the case of one who makes peace between a man and his wife, between family and family, between a man and his fellow, how much more certain is it that punishment will not come upon him (Mekhilta d'Rabbi Yishmael 20:22:2).

ותחללה. הָא לָמַדְתָּ שֶׁאִם הֵנַפְתָּ עָלֶיהָ בַּרְזֶל חִלַּלְתָּ, שֶׁהַמִּזְבֵּחַ נִבְרָא לְהַאֲרִיךְ יָמָיו שֶׁל אָדָם וְהַבַּרְזֶל נִבְרָא לְקַצֵּר יָמָיו שֶׁל אָדָם, אֵין זֶה בַּדִּין שֶׁיּוּנַף הַמְקַצֵּר עַל הַמַּאֲרִיךְ (מכילתא).

ותחללה THEN THOU HAST PROFANED IT — Thus you may learn that if thou liftest up thy iron tool above it thou profanest it. The reason of this it, because the altar is created (its purpose is) to lengthen man’s days and iron has been created (one of its purposes is) to shorten man’s days, it is not right that an object which shortens man’s life should be lifted up above that which lengthens it (Mekhilta, Middoth 3:4). And a further reason it: because the altar makes peace between Israel and their Father in Heaven, and therefore there should not come upon it anything that cuts and destroys. Now, the following statement follows logically, à fortiori: How is it in the case of stones which cannot see nor hear nor speak? Because that they promote peace Scripture ordains, “Thou shalt not lift up against them any iron tool!” Then in the case of one who makes peace between a man and his wife, between family and family, between a man and his fellow, how much more certain is it that punishment will not come upon him (Mekhilta d'Rabbi Yishmael 20:22:2).
R' Ovadiah Yosef, Yechave Da’at Volume 5, Chapter 18 (Summary of Holding)
It is preferable that an armed soldier entering a synagogue to pray cover his weapon with his clothing. If this is not possible, for instance, because he is armed with a large rifle, and there is a great need for him to be carrying his weapon, such as due to security concerns and the like, he may be lenient and enter the synagogue to pray in this manner.
אמר רב אדא בר אהבה אין מוכרין להן עששיות של ברזל מ"ט משום דחלשי מינייהו כלי זיין אי הכי אפילו מרי וחציני נמי אמר רב זביד בפרזלא הינדואה והאידנא דקא מזבנינן א"ר אשי לפרסאי דמגנו עילוון:
Rav Adda bar Ahava says: One may not sell blocks [ashashiot] of iron to gentiles. What is the reason? It is because they forge weapons from them. The Gemara asks: If so, then even hoes and axes should not be sold to them, as they too can be used to forge weapons. Rav Zevid said in response: The ruling of Rav Adda bar Ahava was stated with regard to Indian iron, which is of a superior quality and used only for crafting weapons. The Gemara clarifies: And as for the fact that nowadays we do sell all weapons, Rav Ashi said: We sell the weapons to the Persians, who protect us.
Nimukei Yosef to Avoda Zara 16a
Nowadays (in Talmudic times) we sell weapons [to idolaters] that are fully assembled because they protect us, they fight on our behalf to protect the city and its inhabitants and there is definite [protection from danger], whereas there is only a small possibility that they might use it to harm a member of the Jewish community and this is what we rely on.
כְּשֵׁם שֶׁאֵין מוֹכְרִין לְעוֹבֵד כּוֹכָבִים דְּבָרִים שֶׁמַּחֲזִיקִין בָּהֶן יְדֵיהֶן לַעֲבוֹדַת כּוֹכָבִים כָּךְ אֵין מוֹכְרִין לָהֶם דָּבָר שֶׁיֵּשׁ בּוֹ נֵזֶק לָרַבִּים כְּגוֹן דֻּבִּים וַאֲרָיוֹת וּכְלֵי זַיִן וּכְבָלִים וְשַׁלְשְׁלָאוֹת. וְאֵין מַשְׁחִיזִין לָהֶם אֶת הַזַּיִן. וְכָל שֶׁאָסוּר לְמָכְרוֹ לְעוֹבֵד כּוֹכָבִים אָסוּר לְמָכְרוֹ לְיִשְׂרָאֵל הֶחָשׁוּד לִמְכֹּר לְעוֹבֵד כּוֹכָבִים. וְכֵן אָסוּר לִמְכֹּר כְּלֵי נֵזֶק לְיִשְׂרָאֵל לִסְטִים:
Even as it is forbidden to sell to idolaters things which uphold their hands to idolatry so it is forbidden to sell them things wherein there is a menace to the public, for instance, bears, lions, weapons, iron fetters, and chains; it is likewise forbidden to sharpen their weapons for them. And, everything which is forbidden to sell to an idolater is also forbidden to sell to an Israelite who is under suspicion that he might resell it to an idolater. It is likewise forbidden to sell instruments of harm to robbers who profess to be Israelites.8Ibid. 15a–16b.
הָיוּ יִשְׂרָאֵל שׁוֹכְנִים בֵּין הָעוֹבְדֵי כּוֹכָבִים וְכָרְתוּ לָהֶם בְּרִית מֻתָּר לִמְכֹּר כְּלֵי זַיִן לְעַבְדֵי הַמֶּלֶךְ וְגֵיסוֹתָיו מִפְּנֵי שֶׁעוֹשִׂים בָּהֶם מִלְחָמָה עִם צָרֵי הַמְּדִינָה לְהַצִּילָהּ וְנִמְצְאוּ מְגִנִּים עָלֵינוּ שֶׁהֲרֵי אָנוּ שְׁרוּיִין בְּתוֹכָם. עִיר שֶׁיֵּשׁ בָּהּ עֲבוֹדַת כּוֹכָבִים מֻתָּר לְהַלֵּךְ חוּצָה לָהּ וְאָסוּר לְהִכָּנֵס בְּתוֹכָהּ. הָיָה חוּצָה לָהּ עֲבוֹדַת כּוֹכָבִים מֻתָּר לְהַלֵּךְ בְּתוֹכָהּ:

Israelites living among idolatrous neighbors, with whom they made a covenant of peace, are permitted to sell weapons to the king's servants and militia, because they conduct war therewith against the country's enemies to save it, as a consequence whereof they protect the Israelites who dwell among them. A city wherein there is an established house of idolatry, one is permitted to pass by it without its boundaries, but is forbidden to enter it; if the idolatry is established without its boundaries he may enter it.

(יב) אָסוּר לִמְכֹּר לְעַכּוּ''ם כָּל כְּלֵי הַמִּלְחָמָה וְאֵין מַשְׁחִיזִין לָהֶם אֶת הַזַּיִן וְאֵין מוֹכְרִין לָהֶן לֹא סַכִּין וְלֹא קוֹלָרִין וְלֹא כְּבָלִים [שֶׁל בַּרְזֶל] וְלֹא שַׁלְשְׁלָאוֹת שֶׁל בַּרְזֶל הִינְדּוּאָה וְלֹא דֻּבִּים וַאֲרָיוֹת וְלֹא כָּל דָּבָר שֶׁיֵּשׁ בּוֹ נֵזֶק לָרַבִּים. אֲבָל מוֹכְרִין לָהֶן תְּרִיסִין שֶׁאֵינָן אֶלָּא לְהָגֵן:

(יג) וּכְשֵׁם שֶׁאָסְרוּ לִמְכֹּר לְעַכּוּ''ם כָּךְ אָסְרוּ לִמְכֹּר לְיִשְׂרָאֵל שֶׁמּוֹכֵר לְעַכּוּ''ם. וּמֻתָּר לִמְכֹּר כְּלֵי זַיִן לְחַיִל שֶׁל בְּנֵי הַמְּדִינָה מִפְּנֵי שֶׁהֵן מְגִנִּין עַל יִשְׂרָאֵל:

(12) It is forbidden to sell arms of any kind to heathen ; one should not sharpen their weapons; one should not sell them a knife — — or anything that is likely to be a public danger. Shields, however, may be sold to them, since they are used only for defense.

(13) Just as the sages have prohibited the sale of arms to a heathen, so have they prohibited selling the same to a Jew who sells to a heathen. On the other hand, weapons may be sold to the local citizens' force, since they protect the Jewish population.

מדרבי נתן דתניא רבי נתן אומר מניין שלא יגדל אדם כלב רע בתוך ביתו ואל יעמיד סולם רעוע בתוך ביתו ת"ל (דברים כב, ח) לא תשים דמים בביתך
The justification for this is from the ruling of Rabbi Natan, as it is taught in a baraita: Rabbi Natan says: From where is it derived that one may not raise a vicious dog in his house, and one may not set up an unstable ladder in his house? The verse states: “You shall not bring blood into your house” (Deuteronomy 22:8), i.e., one may not allow a hazardous situation or item to remain in one’s house. As long as the hazard remains, the owner is in violation of this verse and therefore the court may excommunicate him for failing to remove the danger.

אמר רב כהנא אמר רבי שמעון בן לקיש ואמרי לה אמר רב אסי אמר (ריש לקיש) ואמרי לה אמר רבי אבא אמר רבי שמעון בן לקיש כל המגדל כלב רע בתוך ביתו מונע חסד מתוך

Rav Kahana said that Rabbi Shimon ben Lakish said, and some say Rav Asi said that Reish Lakish said, and some say Rabbi Abba said that Rabbi Shimon ben Lakish said: Anyone who raises an evil dog within his home prevents kindness from entering into his home, since poor people will hesitate to enter his house.

ההיא איתתא דעיילא לההוא ביתא למיפא נבח בה כלבא איתעקר ולדה אמר לה מרי דביתא לא תידחלי דשקילי ניביה ושקילין טופריה אמרה ליה שקולא טיבותיך ושדיא אחיזרי כבר נד ולד
The Gemara relates: A certain pregnant woman who entered to use the oven in a certain house to bake, the dog in that house barked at her, and her fetus was displaced. The owner of the house said to her: Do not be afraid because his teeth have been removed and his claws have been removed. She said to him: Take your goodness and throw it on the thorns. Your encouragement is useless as the fetus has already been displaced and will certainly die.

(ו) כל המניח גגו בלא מעקה ביטל מצות עשה ועבר על לא תעשה שנא' ולא תשים דמים בביתך:

(ז) אחד הגג ואחד כל דבר שיש בו סכנה וראוי שיכשול בה אדם וימות כגון שהיתה לו באר (או בור) בחצירו בין שיש בו מים בין שאין בו מים חייב לעשות חוליא גבוה י' טפחים או לעשות לה כיסוי כדי שלא יפול בה אדם וימות:

(ח) וכן כל מכשול שיש בו סכנת נפשות מצות עשה להסירו ולהשמר ממנו ולהזהר בדבר יפה שנאמר השמר לך ושמור נפשך ואם לא הסיר והניח המכשולות המביאים לידי סכנה ביטל מצות עשה ועובר בלא תשים דמים:

(6) All that do not build a fence on their roof violates a positive commandment and a negative commandment. As it says, "do not place blood in your home".

(7) Both a roof or anything dangerous where it's probable that someone will stumble upon and fall, for example if there was a well or a hole in his yard, whether there is water in it or not, one is obligated to make an embankment ten-handbreadths high, or to cover it, lest a person fall into it and die.

(8) Likewise, one has a positive duty to remove and guard oneself of any life-threatening obstacle, as it is said "beware and guard your soul". If one did not removed said obstacles, one has cancelled a positive commandment and transgressed "do not bring bloodguilt" (Deut. 22:8).