Ve'Ahavta LeRe'echa Kamocha
(יח) לֹֽא־תִקֹּ֤ם וְלֹֽא־תִטֹּר֙ אֶת־בְּנֵ֣י עַמֶּ֔ךָ וְאָֽהַבְתָּ֥ לְרֵעֲךָ֖ כָּמ֑וֹךָ אֲנִ֖י יקוק

(18) You shall not take vengeance or bear a grudge against your countrymen. Love your fellow as yourself: I am the LORD.

(ב) ואהבת לרעך כמוך. אָמַר רַבִּי עֲקִיבָא זֶה כְּלָל גָּדוֹל בַּתּוֹרָה (ספרא):

(2) ואהבת לרעך כמוך THOU SHALT LOVE THY FELLOW MAN AS THYSELF —Rabbi Akiba said: “This is a fundamental principle of the Torah” (Sifra, Kedoshim, Chapter 4 12; Talmud Yerushalmi Nedarim 9:3).

(רו) לאהוב כל בני אדם מבני ברית, שנאמר: "וְאָהַבְתָּ לְרֵעֲךָ כָּמוֹךָ" (ויקרא יט, יח).

(206) To love the children of the covenant. Lev. 19.18.

Ramban on Leviticus 19:18:1

(1) The phrase “Love your neighbor as yourself” cannot be meant literally, since man cannot be expected to love his neighbor as himself. Moreover, Rabbi Akiva has ruled that “Your life comes first.” The Torah here enjoins us that we should wish upon our neighbor the same benefits that we wish upon ourselves. Perhaps, this is the reason for the dative instead of the accusative form of the verb phrase; we find the same in “And you shall love him as yourself” (19:34). Indeed, sometimes a person may wish upon his neighbor certain benefits, but only wealth, not wisdom and the like. But even if he wishes his cherished friend well in everything, i.e. wealth, honor, learning, and wisdom, he will not do so unstintingly; he will still insist on a larger share of the benefits. It is this shortcoming that the Torah condemned. Rather, a man should wish his fellow well in everything, just as he does in his own case, and he should place no limitations on his love. Therefore, in the case of Yonatan and David (I Shemuel 20:17), it says that Yonatan “loved him as his own soul,” since he had removed all jealousy from his heart, declaring “And you shall rule over Israel” (ibid. 23:17).

(ג) מִצְוָה עַל כָּל אָדָם לֶאֱהֹב אֶת כָּל אֶחָד וְאֶחָד מִיִּשְׂרָאֵל כְּגוּפוֹ שֶׁנֶּאֱמַר (ויקרא יט יח) "וְאָהַבְתָּ לְרֵעֲךָ כָּמוֹךָ". לְפִיכָךְ צָרִיךְ לְסַפֵּר בְּשִׁבְחוֹ וְלָחוּס עַל מָמוֹנוֹ כַּאֲשֶׁר הוּא חָס עַל מָמוֹן עַצְמוֹ וְרוֹצֶה בִּכְבוֹד עַצְמוֹ. וְהַמִּתְכַּבֵּד בִּקְלוֹן חֲבֵרוֹ אֵין לוֹ חֵלֶק לָעוֹלָם הַבָּא:

(3) It is mandatory upon every man to love each and every one of Israel even as he loves his own self, for it is said: "But thou shalt love thy neighbor as thyself" (Lev. 19.18.). One is therefore, obliged to speak in praise of his neighbor, and to be considerate of his money, even as he is considerate of his own money, or desires to preserve his own honor. "But whosoever glorifies himself in disgracing his neighbor has no share in the world to come" (Yerushalmi, Hegigah. 2.1).3

Contemporary Halakhic Problems, Vol I, Part I, CHAPTER V Medical Questions 10

(10) Nachmanides finds that since the Torah gives permission to seek medical attention the physician's obligation to heal must also be deemed to be inherent in the commandment "And you shall love your neighbor as yourself" (Lev. 19:18).5 The obligation to heal the sick is an instantiation of the general obligation to manifest love and concern for one's neighbor. As such, the obligation to heal encompasses not only situations posing a threat to life or limb or demanding restoration of impaired health but also situations of lesser gravity warranting medical attention for relief of pain and promotion of well-being.

(א) מצות אהבת ישראל - לאהב כל אחד מישראל אהבת נפש, כלומר שנחמל על ישראל ועל ממונו כמו שאדם חומל על עצמו וממונו, שנאמר (ויקרא יט יח) ואהבת לרעך כמוך. ואמרו זכרונם לברכה (שבת לא א) דעלך סני לחברך לא תעביד. ואמרו בספרא (קדושים ד יב) אמר רבי עקיבא זה כלל גדול בתורה, כלומר, שהרבה מצות שבתורה תלויות בכך, שהאוהב חברו כנפשו לא יגנב ממונו ולא ינאף את אשתו, ולא יונהו בממון ולא בדברים, ולא יסיג גבולו, ולא יזיק לו בשום צד, וכן כמה מצות אחרות תלויות בזה. ידוע [גלוי] הדבר לכל בן דעת.

(1) The commandment of love of Israel: To love [with] love of the soul each one of Israel - meaning to say that we have compassion for an Israelite and for his money, [just] like a person has compassion for himself and for his [own] money; as it stated (Leviticus 19:18), "you shall love your neighbor as yourself." And they, may their memory be blessed, said (Shabbat 31a), "What is hateful to you, do not do to your fellow." And they said in Sifra, Kedoshim, Chapter 4:12, "Rabbi Akiva said, 'This is a great principle in the Torah'" - meaning to say that many commandments are dependent upon it. As one that loves his fellow like himself will not steal his money, have adultery with his wife, cheat his money from him nor hurt him from any angle. And so [too,] are there several other commandments dependent on this - the thing is well-known [revealed] to all who have intellect.

Chofetz Chaim, Introduction to the Laws of the Prohibition of Lashon Hara and Rechilut, Positive Commandments 4

(4) (2) And he [the speaker of lashon hara] also transgresses (Vayikra 19:18): "And you shall love your neighbor as yourself," whereby we have been commanded to be as solicitous for our friend's money as we are for our own, and to be solicitous of his honor, and to speak in his praise, as we are solicitous for our own honor. And if one speaks or receives lashon hara and rechiluth against his friend, though it be true, it is apparent that he does not love him at all — how much more so is he in violation of "as yourself!"

English

(פה) וכן כל כיוצא בזה ממיני החריצות שביצר מה שהוא משתדל לפתות את לבות בני האדם. על כן באה התורה וכללה כלל שהכל נכלל בו, (ויקרא יט): ואהבת לרעך כמוך, כמוך בלי שום הפרש, כמוך בלי חילוקים, בלי תחבולות ומזימות, כמוך ממש.

(85) All such arguments are among the diligent efforts of the Yetzer with which he strives to entice the hearts of people. The Torah therefore came and stated a general principle which includes everything: "you shall love your neighbor as yourself" (Vayikra 19:18) - "as yourself", with no difference whatsoever, "as yourself" without any distinction, without strategies and ploys, literally "as yourself".

ר"ע אומר למד תורה בילדותו ילמוד תורה בזקנותו היו לו תלמידים בילדותו יהיו לו תלמידים בזקנותו שנא' בבקר זרע את זרעך וגו' אמרו שנים עשר אלף זוגים תלמידים היו לו לרבי עקיבא מגבת עד אנטיפרס וכולן מתו בפרק אחד מפני שלא נהגו כבוד זה לזה
Rabbi Akiva says that the verse should be understood as follows: If one studied Torah in his youth he should study more Torah in his old age; if he had students in his youth he should have additional students in his old age, as it is stated: “In the morning sow your seed, etc.” They said by way of example that Rabbi Akiva had twelve thousand pairs of students in an area of land that stretched from Gevat to Antipatris in Judea, and they all died in one period of time, because they did not treat each other with respect.

ר׳ עדין שטינזלץ

שנים עשר אלף זוגים (זוגות) תלמידים היו לו לר' עקיבא בחבל הארץ שמגבת עד אנטיפרס בארץ יהודה, וכולן מתו בפרק (זמן) אחד, מפני שלא נהגו כבוד זה לזה.

(ב) ונתחכם יקוק לצוות בענין הנהגת ישראל זע''ז בהדרגה. מצוה א' לא תשנא. ב' לא תקום וגו'. ג' ואהבת, ודקדק לומר, אחיך, עמך, לומר שאין מצוה אלא על אנשים שעושים מעשה עמך, אבל שונאי יקוק כגון המומרים והאפיקורסים אסור לאהוב אותם ואדרבה צריך לשנאותם, כאומר (תהלים קלט) הלא משנאיך יקוק אשנא:
(2) The Torah was very shrewd in giving these directives to the Israelite in a staggered form. 1) First of all, one is not to hate a fellow Jew; 2) next, one is not take revenge for something a fellow Jew has done to him; 3) one is not even to bear a grudge; 4) one is to love one's fellow Jew. The Torah uses 2 different descriptions for a fellow Jew, a) "your brother;" b) "your colleague" or "member of your people." This tells us that the legislation applies only to Jews who basically are Torah-observant but with whom you have a disagreement of a personal nature. If your hatred for them is due to such a Jew displaying his disdain for the Jewish religion one must not only not love them but hate them as we have been told by David in Psalms 139,21 "You know I hate those who hate You, etc."
נזדמן לו אדם אחד שהיה מכוער ביותר אמר לו שלום עליך רבי ולא החזיר לו אמר לו ריקה כמה מכוער אותו האיש שמא כל בני עירך מכוערין כמותך אמר לו איני יודע אלא לך ואמור לאומן שעשאני כמה מכוער כלי זה שעשית כיון שידע בעצמו שחטא ירד מן החמור ונשתטח לפניו ואמר לו נעניתי לך מחול לי אמר לו איני מוחל לך עד שתלך לאומן שעשאני ואמור לו כמה מכוער כלי זה שעשית
He happened upon an exceedingly ugly person, who said to him: Greetings to you, my rabbi, but Rabbi Elazar did not return his greeting. Instead, Rabbi Elazar said to him: Worthless [reika] person, how ugly is that man. Are all the people of your city as ugly as you? The man said to him: I do not know, but you should go and say to the Craftsman Who made me: How ugly is the vessel you made. When Rabbi Elazar realized that he had sinned and insulted this man merely on account of his appearance, he descended from his donkey and prostrated himself before him, and he said to the man: I have sinned against you; forgive me. The man said to him: I will not forgive you go until you go to the Craftsman Who made me and say: How ugly is the vessel you made.