דן לכף זכות

לֹא־תַעֲשׂ֥וּ עָ֙וֶל֙ בַּמִּשְׁפָּ֔ט לֹא־תִשָּׂ֣א פְנֵי־דָ֔ל וְלֹ֥א תֶהְדַּ֖ר פְּנֵ֣י גָד֑וֹל בְּצֶ֖דֶק תִּשְׁפֹּ֥ט עֲמִיתֶֽךָ׃

Leviticus 19:15

You shall not render an unfair decision: do not favor the poor or show deference to the rich; judge your kinsman fairly.

שבועות ל׳ א:י״ב

ת"ר "בצדק תשפוט עמיתך" שלא יהא אחד יושב ואחד עומד אחד מדבר כל צרכו ואחד אומר לו קצר דבריך. ד"א בצדק תשפוט עמיתך הוי דן את חבירך לכף זכות.

Shevuot 30a:12

The Sages taught: The verse states: “But in righteousness shall you judge your colleague” (Leviticus 19:15), from which it is derived: The court must ensure that there will not be a situation where one litigant is sitting and one litigant is standing, or a situation where one litigant says everything that he needs to say to present his case and one litigant, the judge says to him: Curtail your statement. Alternatively, it is derived from the verse: “But in righteousness shall you judge your colleague,” that you should judge another favorably, and seek to find justification for his actions, even if when interpreted differently his actions could be judged unfavorably.

משנה אבות א׳:ו׳

יְהוֹשֻׁעַ בֶּן פְּרַחְיָה וְנִתַּאי הָאַרְבֵּלִי קִבְּלוּ מֵהֶם. יְהוֹשֻׁעַ בֶּן פְּרַחְיָה אוֹמֵר, עֲשֵׂה לְךָ רַב, וּקְנֵה לְךָ חָבֵר, וֶהֱוֵי דָן אֶת כָּל הָאָדָם לְכַף זְכוּת:

Pirkei Avot 1:6

Joshua ben Perahiah and Nittai the Arbelite received [the oral tradition] from them. Joshua ben Perahiah used to say: appoint for thyself a teacher, and acquire for thyself a companion and judge all men with the scale weighted in his favor.

Q: Does one always have to be דן לכף זכות?

רש"י על שבועות ל׳ א:י״ב:א׳

הוי דן את חבירך לכף זכות: ולא בדין בעלי דינים הכתוב מדבר אלא ברואה חבירו עושה דבר שאתה יכול להכריעו לצד עבירה ולצד זכות הכריעו לזכות ואל תחשדהו בעבירה:

Rashi on Shevuot 30a:12:1

...

רבינו יונה על פרקי אבות א׳:ו׳:ד׳

זה מדבר עם אדם שאין יודעין בו אם הוא צדיק ואם הוא רשע. ואם מכירין אותו והוא איש בינוני פעמים עושה רע ופעמים עושה טוב ואם יעשה דבר שיש לדונו לכף חובה ויש לדונו לזכות בשיקול או אפילו כפי הנראה נוטה לכף חובה יותר. אם משום צד ענין יכול לדונו לזכות יש לו לומר לטובה נתכוון. אבל אין הדברים בצדיק גמור ולא ברשע גמור. כי הצדיק אפי' במעשה שכלו רע ונוטה לכף חובה מכל עבר ידינהו לטובה לאמר כי שגגה היתה... גם מן הרשע הגמור לא אמר, אפי' מעשהו כלו טוב ואין נראה לחוש עליו משום צד עון יש לאדם לדונו לכף חובה ולומר לפנים עשה ואין תוכו כברו.

Rabbeinu Yonah on Pirkei Avot 1:6:4

(4) "and judge every person as meritorious": This is speaking about a person about whom we do not know if he is righteous or if he is evil; or if we know that he is a moderate person, sometimes doing evil and sometimes doing good. And if he does something that can make us judge him unfavorably and [also] judge him favorably in our understanding - or even if, (towards) according to what appears, it leans more towards the side of guilt - if he can judge him favorably from one aspect of the matter, he should say, "His intentions were good." But these words are not [applicable] to the completely righteous or the completely evil. As with the righteous person, even with an action that is completely evil and leans toward guilt in every aspect, we should judge him favorably and say, "'It was a mistake that came out from the hand of the ruler,' and behold he regretted and observed [it] and [already] requested forgiveness." And it is like the sages, may their memory be blessed, said (Berakhot 19a), "If you see a Torah scholar who sinned at night, do not ruminate about him during the day, lest he has repented. 'Lest' comes into your mind? But rather, I will say he certainly repented." The explanation of "'Lest' comes into your mind?" is that since he is a Torah scholar and up until now, no corrupt thing has come to his hand; he certainly repented right away. You behold [from here that] one should never judge the perfectly righteous person unfavorably. And about him there is no reason to say, "judge every person as meritorious." And he also did not speak about the completely evil person. Even if his actions are completely good and it is not evident to be concerned about him regarding an angle of iniquity, a person should judge him unfavorably and say, "He did it on the surface 'and his inside is not like his outside.'" And it is like it is stated (Proverbs 26:25), "Though he be fair-spoken do not trust him, for seven abominations are in his heart." And so [too] wrote Rambam, may his memory be blessed. And about this Shlomo stated in his wisdom (Proverbs 21:12), "The righteous one observes the house of the wicked man; he subverts the wicked to the bad." He meant to say, people think that because the righteous do not know how to do evil, [hence] they do not recognize they ways of the evil - as they do not understand those that do it. And the matter is not like this, as 'the righteous one observes the house of the wicked,' and knows and recognizes and monitors the evil of his ways more than other people who know [about it], but don't pay attention to it. "He subverts the wicked to the bad" - when the righteous person sees the action of the evildoers which appear to be in a good path, he subverts it and pushes it towards his judgment to say that he has done wrong - since he did not intend [to do] a commandment, but rather to place himself among those assumed to be good.

משנה תורה, הלכות תשובה ד׳:ד׳

וּמֵהֶן חֲמִשָּׁה דְּבָרִים הָעוֹשֶׂה אוֹתָן אֵין חֶזְקָתוֹ לָשׁוּב מֵהֶן. לְפִי שֶׁהֵם דְּבָרִים קַלִּים בְּעֵינֵי רֹב הָאָדָם וְנִמְצָא חוֹטֵא וְהוּא יְדַמֶּה שֶׁאֵין זֶה חֵטְא. וְאֵלּוּ הֵן... וְהַחוֹשֵׁד כְּשֵׁרִים אוֹמֵר בְּלִבּוֹ שֶׁאֵינוֹ חֵטְא לְפִי שֶׁהוּא אוֹמֵר מֶה עָשִׂיתִי לוֹ וְכִי יֵשׁ שָׁם אֶלָּא חֲשָׁד שֶׁמָּא עָשָׂה אוֹ לֹא עָשָׂה וְהוּא אֵינוֹ יוֹדֵעַ שֶׁזֶּה עָוֹן שֶׁמֵּשִׂים אָדָם כָּשֵׁר בְּדַעְתּוֹ כְּבַעַל עֲבֵרָה:

Mishneh Torah, Repentance 4:4

(4) And, there are, furthermore, five transgressions among this group of twenty-four, the presumption of one who commits each and every one of them being against his inclination to turn toward repentance, because the majority of people consider them of minor importance, as a consequence whereof one stoops in sin imagining that what he does is no sin at all. They are: (1) he who dines at a table knowing that the meal is of insufficient quantity to satisfy even the appetite of the host, for such is an offshoot of robbery, whereas he imagines, saying: "Have I not eaten with the consent of the host?" (2) he who makes use of a poor man's pledge, for a poor man's pledge is none else save an article such as an axe or plough, whereas he will say in his imagination: "Nothing thereof was diminished, I have not robbed him"; (3) he who wantonly stares at the opposite sex, for he thinks that it is of no matter, saying: "Have I stilled an urge, or even been near her"? whereas he remains oblivious to the fact that purposeful eye-staring is a great iniquity and begets actual unchastity, even as it is said: "And that ye seek not after your own heart and your own eyes" (Num. 15.39); (4) he who acquires honor by disgracing his neighbor, for he thinks that he committed no sin, as his neighbor stood not by, and did not feel the shame, as he did not insult him personally, save by comparing his own good conduct and his own education against the conduct of his neighbor or his education so that the audience may infer that he is honorable and his neighbor disgraceful; (5) he who casts suspicion upon the upright, for he thinks within his heart that he sinned not, saying to himself: "What have I done to him, is there anything more to it than mere suspicion? perhaps he did it, and perhaps he did it not;" whereas he does realize that this is an iniquity to place an upright man in his mind on the same level with an evil-doer.⁷Ibid. G.

שבת קכ״ז ב:ב׳-ה׳

תָּנוּ רַבָּנַן: הַדָּן חֲבֵירוֹ לְכַף זְכוּת דָּנִין אוֹתוֹ לִזְכוּת.

וּמַעֲשֶׂה בְּאָדָם אֶחָד שֶׁיָּרַד מִגָּלִיל הָעֶלְיוֹן וְנִשְׂכַּר אֵצֶל בַּעַל הַבַּיִת אֶחָד בַּדָּרוֹם שָׁלֹשׁ שָׁנִים. עֶרֶב יוֹם הַכִּפּוּרִים אָמַר לוֹ: תֵּן לִי שְׂכָרִי, וְאֵלֵךְ וְאָזוּן אֶת אִשְׁתִּי וּבָנַי. אָמַר לוֹ: אֵין לִי מָעוֹת. אָמַר לוֹ: תֵּן לִי פֵּירוֹת. אָמַר לוֹ: אֵין לִי. תֵּן לִי קַרְקַע — אִין לִי. תֵּן לִי בְּהֵמָה — אֵין לִי. תֵּן לִי כָּרִים וּכְסָתוֹת — אֵין לִי. הִפְשִׁיל כֵּלָיו לַאֲחוֹרָיו, וְהָלַךְ לְבֵיתוֹ בְּפַחֵי נֶפֶשׁ.

לְאַחַר הָרֶגֶל נָטַל בַּעַל הַבַּיִת שְׂכָרוֹ בְּיָדוֹ, וְעִמּוֹ מַשּׂוֹי שְׁלֹשָׁה חֲמוֹרִים, אֶחָד שֶׁל מַאֲכָל, וְאֶחָד שֶׁל מִשְׁתֶּה, וְאֶחָד שֶׁל מִינֵי מְגָדִים, וְהָלַךְ לוֹ לְבֵיתוֹ. אַחַר שֶׁאָכְלוּ וְשָׁתוּ נָתַן לוֹ שְׂכָרוֹ. אָמַר לוֹ: בְּשָׁעָה שֶׁאָמַרְתָּ לִי ״תֵּן לִי שְׂכָרִי״ וְאָמַרְתִּי ״אֵין לִי מָעוֹת״, בַּמֶּה חֲשַׁדְתַּנִי? אָמַרְתִּי: שֶׁמָּא פְּרַקְמַטְיָא בְּזוֹל נִזְדַּמְּנָה לְךָ, וְלָקַחְתָּ בָּהֶן. וּבְשָׁעָה שֶׁאָמַרְתָּ לִי ״תֵּן לִי בְּהֵמָה״, וְאָמַרְתִּי ״אֵין לִי בְּהֵמָה״, בַּמֶּה חֲשַׁדְתַּנִי? אָמַרְתִּי: שֶׁמָּא מוּשְׂכֶּרֶת בְּיַד אֲחֵרִים. בְּשָׁעָה שֶׁאָמַרְתָּ לִי ״תֵּן לִי קַרְקַע״, וְאָמַרְתִּי לְךָ ״אֵין לִי קַרְקַע״, בַּמֶּה חֲשַׁדְתַּנִי? אָמַרְתִּי: שֶׁמָּא מוּחְכֶּרֶת בְּיַד אֲחֵרִים הִיא. וּבְשָׁעָה שֶׁאָמַרְתִּי לְךָ ״אֵין לִי פֵּירוֹת״ בַּמֶּה חֲשַׁדְתַּנִי? אָמַרְתִּי: שֶׁמָּא אֵינָן מְעוּשָּׂרוֹת. וּבְשָׁעָה שֶׁאָמַרְתִּי לְךָ ״אֵין לִי כָּרִים וּכְסָתוֹת״ בַּמֶּה חֲשַׁדְתַּנִי? אָמַרְתִּי: שֶׁמָּא הִקְדִּישׁ כָּל נְכָסָיו לַשָּׁמַיִם. אָמַר לוֹ: הָעֲבוֹדָה! כָּךְ הָיָה. הִדַּרְתִּי כׇּל נְכָסַי בִּשְׁבִיל הוּרְקָנוֹס בְּנִי שֶׁלֹּא עָסַק בַּתּוֹרָה. וּכְשֶׁבָּאתִי אֵצֶל חֲבֵירַי בַּדָּרוֹם הִתִּירוּ לִי כָּל נְדָרַי. וְאַתָּה, כְּשֵׁם שֶׁדַּנְתַּנִי לִזְכוּת, הַמָּקוֹם יָדִין אוֹתְךָ לִזְכוּת.

Shabbat 127b:2-5

The Sages taught in a baraita: One who judges another favorably is himself judged favorably. And there was an incident involving a certain person who descended from the Upper Galilee and was hired to work for a certain homeowner in the South for three years. On the eve of the Day of Atonement, he said to the homeowner: Give me my wages, and I will go and feed my wife and children. The homeowner said to him: I have no money. He said to him: In that case, give me my wages in the form of produce. He said to him: I have none. The worker said to him: Give me my wages in the form of land. The homeowner said to him: I have none. The worker said to him: Give me my wages in the form of animals. He said to him: I have none. The worker said to him: Give me cushions and blankets. He said to him: I have none. The worker slung his tools over his shoulder behind him and went to his home in anguish. After the festival of Sukkot, the homeowner took the worker’s wages in his hand, along with a burden that required three donkeys, one laden with food, one laden with drink, and one laden with types of sweets, and went to the worker’s home. After they ate and drank, the homeowner gave him his wages. The homeowner said to him: When you said to me: Give me my wages, and I said: I have no money, of what did you suspect me? Why did you not suspect me of trying to avoid paying you? The worker answered, I said: Perhaps the opportunity to purchase merchandise [perakmatya] inexpensively presented itself, and you purchased it with the money that you owed me, and therefore you had no money available. The homeowner asked: And when you said to me: Give me animals, and I said: I have no animals, of what did you suspect me? The worker answered: I said: Perhaps the animals are hired to others. The homeowner asked: When you said to me: Give me land, and I said: I have no land, of what did you suspect me? The worker answered: I said: Perhaps the land is leased to others, and you cannot take the land from the lessees. The homeowner asked: And when you said to me: Give me produce, and I said: I have no produce, of what did you suspect me? The worker answered: I said: Perhaps they are not tithed, and that was why you could not give them to me. The homeowner asked: And when I said: I have no cushions or blankets, of what did you suspect me? The worker answered: I said: Perhaps he consecrated all his property to Heaven and therefore has nothing available at present. The homeowner said to him: I swear by the Temple service that it was so. I had no money available at the time because I vowed and consecrated all my property on account of Hyrcanus, my son, who did not engage in Torah study. The homeowner sought to avoid leaving an inheritance for his son. And when I came to my colleagues in the South, the Sages of that generation, they dissolved all my vows. At that point, the homeowner had immediately gone to pay his worker. Now the homeowner said: And you, just as you judged favorably, so may God judge you favorably.

שבת קכ״ז ב:ו׳-ט׳

תָּנוּ רַבָּנַן: מַעֲשֶׂה בְּחָסִיד אֶחָד שֶׁפָּדָה רִיבָה אַחַת בַּת יִשְׂרָאֵל, וְלַמָּלוֹן הִשְׁכִּיבָהּ תַּחַת מַרְגְּלוֹתָיו. לְמָחָר יָרַד וְטָבַל וְשָׁנָה לְתַלְמִידָיו. וְאָמַר לָהֶן: בְּשָׁעָה שֶׁהִשְׁכַּבְתִּיהָ תַּחַת מַרְגְּלוֹתַי, בַּמֶּה חֲשַׁדְתּוּנִי? אָמַרְנוּ: שֶׁמָּא יֵשׁ בָּנוּ תַּלְמִיד שֶׁאֵינוֹ בָּדוּק לְרַבִּי. בְּשָׁעָה שֶׁיָּרַדְתִּי וְטָבַלְתִּי, בַּמֶּה חֲשַׁדְתּוּנִי? אָמַרְנוּ: שֶׁמָּא מִפְּנֵי טוֹרַח הַדֶּרֶךְ אֵירַע קֶרִי לְרַבִּי. אָמַר לָהֶם: הָעֲבוֹדָה! כָּךְ הָיָה. וְאַתֶּם, כְּשֵׁם שֶׁדַּנְתּוּנִי לְכַף זְכוּת, הַמָּקוֹם יָדִין אֶתְכֶם לְכַף זְכוּת.

Shabbat 127b:6-9

On a similar note, the Gemara relates that the Sages taught in a baraita: There was an incident involving a certain pious man who redeemed a young Jewish woman from captivity. When they arrived at the inn he had her lie beneath his feet. The next day, he descended, and immersed in a ritual bath to purify himself before Torah study and prayer, and taught his students. This conduct could arouse suspicion that the pious man kept the maiden for himself, as immersion in the morning is customary for men who have experienced a seminal emission by engaging in sexual relations. And the pious man said to his students: When I had her lie beneath my feet, of what did you suspect me? They said to him: We said: Perhaps there is a student among us whose conduct is not established before the rabbi, and he wanted to make certain that this student would not inappropriately accost the young woman. Therefore, the rabbi kept the woman close by. He said to them: When I descended and immersed, of what did you suspect me? They answered: Perhaps due to the exertion of travel, a seminal emission befell the rabbi. He said to them: I swear by the Temple service that it was so. And you, just as you judged me favorably, so may God judge you favorably. The Sages taught a similar baraita: Once there was a certain matter needed by Torah scholars. They wanted to discuss an issue with a certain matron whose company was kept by all the prominent people of Rome. The Torah scholars wanted to address the government on behalf of the Jewish people, and they sought the matron’s advice. They said: Who will go? Rabbi Yehoshua said to them: I shall go.

שבת קכ״ז ב:ט׳-י״ג

תָּנוּ רַבָּנַן: פַּעַם אַחַת הוּצְרַךְ דָּבָר אֶחָד לְתַלְמִידֵי חֲכָמִים אֵצֶל מַטְרוֹנִיתָא אַחַת שֶׁכׇּל גְּדוֹלֵי רוֹמִי מְצוּיִין אֶצְלָהּ. אָמְרוּ: מִי יֵלֵךְ? אָמַר לָהֶם רַבִּי יְהוֹשֻׁעַ: אֲנִי אֵלֵךְ. הָלַךְ רַבִּי יְהוֹשֻׁעַ וְתַלְמִידָיו. כֵּיוָן שֶׁהִגִּיעַ לְפֶתַח בֵּיתָהּ, חָלַץ תְּפִילָּיו בְּרִחוּק אַרְבַּע אַמּוֹת, וְנִכְנַס וְנָעַל הַדֶּלֶת בִּפְנֵיהֶן. אַחַר שֶׁיָּצָא, יָרַד וְטָבַל וְשָׁנָה לְתַלְמִידָיו. וְאָמַר לָהֶן: בְּשָׁעָה שֶׁחָלַצְתִּי תְּפִילִּין, בַּמֶּה חֲשַׁדְתּוּנִי? אָמַרְנוּ: כְּסָבוּר רַבִּי, לֹא יִכָּנְסוּ דִּבְרֵי קְדוּשָּׁה בִּמְקוֹם טוּמְאָה. בְּשָׁעָה שֶׁנָּעַלְתִּי, בַּמֶּה חֲשַׁדְתּוּנִי? אָמַרְנוּ: שֶׁמָּא דְּבַר מַלְכוּת יֵשׁ בֵּינוֹ לְבֵינָהּ. בְּשָׁעָה שֶׁיָּרַדְתִּי וְטָבַלְתִּי בַּמֶּה חֲשַׁדְתּוּנִי, אָמַרְנוּ: שֶׁמָּא נִיתְּזָה צִינּוֹרָא מִפִּיהָ עַל בְּגָדָיו שֶׁל רַבִּי. אָמַר לָהֶם: הָעֲבוֹדָה! כָּךְ הָיָה. וְאַתֶּם, כְּשֵׁם שֶׁדַּנְתּוּנִי לִזְכוּת, הַמָּקוֹם יָדִין אֶתְכֶם לִזְכוּת.

Shabbat 127b:9-13

The Sages taught a similar baraita: Once there was a certain matter needed by Torah scholars. They wanted to discuss an issue with a certain matron whose company was kept by all the prominent people of Rome. The Torah scholars wanted to address the government on behalf of the Jewish people, and they sought the matron’s advice. They said: Who will go? Rabbi Yehoshua said to them: I shall go. Rabbi Yehoshua and his students went to her. When he arrived with his students at the entrance of her house, he removed his phylacteries at a distance of four cubits from the door, and entered, and locked the door before them. After he emerged, he descended and immersed in a ritual bath, and taught his students. Here too, this was conduct that could arouse suspicion that something improper transpired. And he said to his students: When I removed the phylacteries, of what did you suspect me? They said to him, we said: The rabbi must hold that sacred items may not enter a place of impurity. Therefore, it would have been inappropriate to enter the house with phylacteries. He asked: When I locked the door, of what did you suspect me? They said to him: We said: Perhaps there is a discreet royal matter that must be discussed between him and her and should not be revealed. Rabbi Yehoshua asked: When I descended and immersed, of what did you suspect me? They said to him, we said: Perhaps a bit of spittle sprayed from her mouth onto the rabbi’s clothes. The Sages decreed that the legal status of a gentile is like that of a zav; their bodily fluids transmit ritual impurity. Rabbi Yehoshua said to them: I swear by the Temple service that it was so. And you, just as you judged favorably, so may God judge you favorably.

Is there a חיוב to be דן לכף זכות, or is it just a מדת חסידות.

ספר המצוות, מצוות עשה קע״ז:א׳

ובכללה גם כן שיתחייב שידון את חבירו לכף זכות ולא יפרש מעשיו ודבריו אלא לטוב.

Sefer HaMitzvot, Positive Commandments 177:1

That is that He commanded all judges to equalize the litigants, that each of them be heard - whether his words are long or short. And that is His, may He be exalted, saying, "with righteousness shall you judge your fellow" (Leviticus 19:15). And the explanation appears in the [Sifra] (Sifra, Kedoshim, Chapter 4:4) - "that one not be allowed to speak at length, and the other told, 'Speak briefly.'" And that is one of the intentions included in the command. And it also comes [to teach] that each person is commanded to judge an argument between two litigants [according to] Torah law, if he knows [the law]. And they said in explanation (Sanhedrin 3a), "By Torah law, one must judge one's fellow - as it is stated, 'with righteousness shall you judge your fellow.'" And also included in it is that one is obligated to judge his fellow favorably and interpret his actions and his words only for the good. And the regulations of this commandment have already been explained in scattered places in the Talmud. (See Parashat Kedoshim; Mishneh Torah, The Sanhedrin and the Penalties within their Jurisdiction 21.)

רמב"ם משנה אבות א׳:ו׳:ב׳

והוי דן את כל האדם לכף זכות: וכשיהיה בלתי ידוע והמעשה בלתי מכריע לא' משני הקצוות צריך בדרך החסידות שתדין לכף זכות איזה קצה שיהיה משני הקצוות:

Rambam on Pirkei Avot 1:6:2

"and judge every person as meritorious:" Its subject is when there is a person whom you do not about him if he is righteous or if he is wicked and you see him doing an act or saying something and if you interpret it one way it will be good and if you interpret in another way it will be bad - [in this case,] take it to the good and do not think bad about it. But if the man is known to be famously righteous and of good deeds; and an action of his is seen that all of its aspects indicate that it is a bad deed and a person can only determine it to be good with great stretching and a distant possibility, it is fit that you take it that it is good, since there is some aspect of a possibility that it is good. And it is not permissible for you to suspect him; and about this did they say (Shabbat 97a), "The body of anyone who suspects proper ones will be struck." And so [too] when it is an evildoer and his deeds are famous, and afterwords we see him that he does a deed, all of the indications about which are that it is good but there is an aspect of a distant possibility that it is bad; it is fit to guard oneself from him and not to believe that it is good, since there is a possibility for the bad. And about this is it stated (Proverbs 26:25), (Also) "Though he be fair-spoken do not trust him, etc." But when he is not known and the deed is indeterminate towards one of the two extremes; according to the ways of piety, one must judge a person as meritorious towards whichever extreme of the two extremes [would be the case].

שבועות ל׳ א:י״ב

ת"ר ״בצדק תשפוט עמיתך״ הוי דן את חבירך לכף זכות

Shevuot 30a:12

משנה אבות א׳:ו׳

(ו) יְהוֹשֻׁעַ בֶּן פְּרַחְיָה וְנִתַּאי הָאַרְבֵּלִי קִבְּלוּ מֵהֶם. יְהוֹשֻׁעַ בֶּן פְּרַחְיָה אוֹמֵר, עֲשֵׂה לְךָ רַב, וּקְנֵה לְךָ חָבֵר, וֶהֱוֵי דָן אֶת כָּל הָאָדָם לְכַף זְכוּת:

Pirkei Avot 1:6

(6) Joshua ben Perahiah and Nittai the Arbelite received [the oral tradition] from them. Joshua ben Perahiah used to say: appoint for thyself a teacher, and acquire for thyself a companion and judge all men with the scale weighted in his favor.

Q: Why is there a חיוב to be דן לכף זכות?

ספר החינוך רל״ה:ב׳

במה שאמרנו שכל אדם חיב לדון חברו לכף זכות, שהוא בכלל המצוה, יהיה סבה להיות בין אנשים שלום ורעות, ונמצא שעקר כל כונת המצוה להועיל בישוב בני אדם עם ישר הדין ולתת ביניהם שלום עם סלוק החשד איש באיש.

Sefer HaChinukh 235:2

The root of the commandment is revealed to all - as with equitability in judgement, the world is civilized. But if a judge honors one of the litigants over the other, the [latter] disputant will fear to say all of his claims in front of him. And from this, the judgement will come out twisted. And about that which we said that it is a commandment upon one wise in words of Torah - and he be a righteous man - to judge those who disagree, that this is included in the commandment as well; there is benefit in this as well, as he will judge a true judgement. But if this one that knows does not want to judge, other people who are not wise will judge them, and they will slant the judgement towards one of the litigants without knowing. Also about that which we said that every person is obligated to judge his fellow favorably - that it is included in the commandment - is a cause for there to be peace and amity among people. And [so] it comes out that the essence of the whole intent of the commandment is to help in the civilization of people with righteousness of judgement, and to bring peace among them with the removal of suspicion of one man towards another.

משנה אבות א׳:ו׳

(ו) יְהוֹשֻׁעַ בֶּן פְּרַחְיָה וְנִתַּאי הָאַרְבֵּלִי קִבְּלוּ מֵהֶם. יְהוֹשֻׁעַ בֶּן פְּרַחְיָה אוֹמֵר, עֲשֵׂה לְךָ רַב, וּקְנֵה לְךָ חָבֵר, וֶהֱוֵי דָן אֶת כָּל הָאָדָם לְכַף זְכוּת:

Pirkei Avot 1:6

דרך חיים א׳:ו׳:א׳-ד׳

ולפיכך אמר "והוי דן את כל אדם לכף זכות", כי הרב והחבר מה שהם רגילים עם האדם, אי אפשר שלא יחשוב בעיניו שחטא לו, כי כל ענינו עמו, ויבא לידי פירוד. לכך אמר על זה "והוי דן את כל אדם לכף זכות", וכאשר אתה דן אותו לכף זכות, לא יבא פירוד בינך ובין רבך ובין חבירך, כי תדין אותו לכף זכות כאשר אתה חושב שעשה דבר כנגדך.

Derekh Chayyim 1:6:1-4

...

ספר מצוות קטן רכ״ד:ב׳

ואמרינן כי בכלל זה לדון חבירו לכף זכות שמתוך שידונו לכף זכות - יחשוב ״אין חוטא רק אני״ וישוב לבוראו.

Sefer Mitzvot Katan 224:2

...

משנה אבות א׳:ז׳

נִתַּאי הָאַרְבֵּלִי אוֹמֵר, הַרְחֵק מִשָּׁכֵן רָע, וְאַל תִּתְחַבֵּר לָרָשָׁע, וְאַל תִּתְיָאֵשׁ מִן הַפֻּרְעָנוּת:

Pirkei Avot 1:7

Nittai the Arbelite used to say: keep a distance from an evil neighbor, do not become attached to the wicked, and do not abandon faith in [divine] retribution.

:נפקא מינה בין חינוך וסמ״ק
1. מחילה
2. דן לכף זכות על מיתים
3. אם יש חיוב לדן כל אדם לכף זכות או רק חברים