LEV456 If the person who sinned is considered an average Jew who is usually careful to avoid transgressing and stumbles only occasionally, then the halachah is as follows. If it is possible that the person sinned unintentionally, or was not aware that this act was forbidden, or thought that it was a mere stringency or a good practice that pious individuals are careful about, and even if one saw him repeatedly violate the prohibition, one should definitely give him the benefit of the doubt and assume that he sinned because of one of the aforementioned reasons. Therefore, it is forbidden to tell others what happened to, lest the other person will be disgraced in their eyes. Furthermore, even the person who witnessed the transgression should not look down upon the other person. It is forbidden for him to hate the other person because of what he saw, for he is required to judge him favorably. According to many poskim, this is included in the positive Torah commandment of בְּצֶ֖דֶק תִּשְׁפֹּ֥ט עֲמִיתֶֽךָ, “Judge your fellow favorably” (Vayikra 19:15). However, if one sees a person violate a well- known prohibition-- such as immorality, or eating forbidden foods, or any other similar prohibition--in which case it would seem that the person who sinned was aware of the prohibition and intentionally violated it, then halachah is as follows. If that person is otherwise considered an average Jew, who is usually careful about sinning and was seen transgressing this prohibition only once, in private, then it is forbidden to tell others about his transgression even if he is not present. One who reveals the incident to others commits a serious offense, for perhaps the person has already mended his wrongful ways and regrets his misdeed. In that case, Hashem has already forgiven him, since he has fulfilled the primary requirement of teshuvah, which is heart-felt regret. If someone publicizes that person's sin, then the person will be disgraced in the eyes of the listeners even though he already regretted his misdeed and was forgiven for it. Therefore, the evildoer who speaks about this person's misdeed is himself guilty of a grave sin .... One should rebuke the person privately for defying Hashem by committing this offense, and caution him to avoid those things that brought him to sin, so that he will not repeat the sin in the future. When he rebukes the other person, he should make sure to speak softly so as not to embarrass him, as it says:הֹוכֵ֤חַ תֹּוכִ֙יחַ֙ אֶת־עֲמִיתֶ֔ךָ וְלֹא־תִשָּׂ֥א עָלָ֖יו חֵֽטְא׃, “You shall surely rebuke your fellow, but do not bear a sin because of him [by shaming him] (Vayikra 19:17).