Musar zu Wajikra 19:15

“You shall do no unrighteousness in judgment” (Leviticus 19:15). Behold, afterward it states, “you shall not favor the poor or show deference to the rich; judge your countryman fairly.” So what is, “judgement” stated at the beginning of the verse? Our Rabbis, may their memory be blessed, said (Sifra, Kedoshim, Chapter 8:5) [that] this is [referring to] length, weight and capacity: “It is to teach us that a measurer is called a judge, and if he falsifies in measurement (it is as if the perverts justice); and he is called wrong, [...], revolting, rejected and abominable, and he brings about five things (like one who perverts justice): He defiles the (Land), he profanes the Name, he drives out the Divine Presence, he causes Israel to fall by the sword, and he exiles them from their land.” (And it appears to me that there is a lacuna here - and it is accordingly found below - “You shall not falsify measures of length, weight, or capacity. You shall have an honest balance, honest weights, an honest ephah, and an honest hin; I am the Lord, your God, who freed you, etc.” [Leviticus 19:35-36]). “Measures of length” - that is measuring of land; “weight” - like its meaning; “or capacity” - that is a liquid and a dry measure; “honest weights” - masses to weigh across from them; “an ephah” is a dry measure; “a hin” is a liquid measure; “I am the Lord, your God, who freed you, etc.” - in Egypt, I distinguished between the drop of a firstborn and the drop that was not a firstborn, so I am credible to punish the one who hides his weights in salt, in order to fool the creatures who are not aware of them.

And you must know that the punishment of the fool that advocates guilt is only when he attributes a defect in a man who fears sin, [and] whose [evil] impulse seized him and he sinned and was guilty - as his practice and way is to regret his sins. And all the more so if the matter that he repented is known. But [regarding] the man whose path you have examined and he has no fear of God in front of his eyes and is also stationed on the bad path - it is a commandment to speak in his disgrace and to reveal his sins, and to make the ones involved with sin foul in the eyes of people, so that the souls of the ones listening will be revolted from bad deeds. And it is stated (Proverbs 29:27), “The unjust man is an abomination to the righteous.” And it is [also] stated (Proverbs 8:13), “To fear the Lord is to hate evil.” And they said (Sanhedrin 52a), “It is permissible to call an evildoer who is the son of a righteous man, ‘an evildoer, son of an evildoer’; and it is permitted to call a righteous man who is the son of an evildoer, ‘a righteous man, son of a righteous man.’”
And behold when you see a man who is saying something or performing an act, and one can judge the thing as him being guilty or being innocent: If the man is one that fears God, you have been obligated to judge him favorably in truth - even if the thing is closer to, and makes more sense to be, understood unfavorably. And if he is from the [group] in-between, that are careful about sin, but sometimes stumble over it - you must incline the doubt towards judging favorably, as our Rabbis, may their memory be blessed, said (Shabbat 127b), “One who judges another favorably is himself judged favorably.” And it is a positive commandment from the Torah, as it is stated (Leviticus 19:15), “you shall judge your countryman justly (betsedek, which can also be understood as, favorably).” And if the matter leans towards guilt - let the matter be a doubt to you, and do not decide it unfavorably. But if most of that man’s actions are evil, or you have examined that he has no fear of God in his heart - judge his actions or his words unfavorably, as it is stated (Proverbs 21:12), “The Righteous One observes the house of the wicked man; he subverts the wicked to their ruin.” And we have already discussed its explanation.

One should also accustom himself to judge his friend in the scales of merit, as Chazal have said (Shevuoth 30a): "(Vayikra 19:15): 'In righteousness shall you judge your friend' — Judge your friend in the scales of merit." And this is one of the things for which one eats the fruits in this world, with the principal remaining for the world to come, as they said in Shabbath 127a.