Reprinted with permission from Louis Jacobs, The Jewish Religion: A Companion, published by Oxford University Press.
The source for the obligation to offer reproof to a neighbor is the verse, “Thou shalt not hate thy brother in thine heart: thou shalt surely rebuke thy neighbor and not suffer sin because of him” (Leviticus 19:17). The plain meaning of the verse is: if you believe that your neighbor has wronged you, do not keep silent and hate him in your heart, but [instead] rebuke him for his offense and have done with it. It is as if the verse is saying: if you bear a grudge against someone, get it off your chest and then forget about it, instead of bottling it up inside you and going about with hatred seething in your heart.
But the Rabbis extend the obligation to offer rebuke whenever a neighbor has committed or intends to commit any offense, whether ethical or religious, as the prophets rebuked the people for their shortcomings. This is based on the principle that all Jews are responsible for one another, so that to fail to offer rebuke when it is needed is to participate in the offense. The conclusion of the verse is understood to mean: if you rebuke him for his sins, all well and good, but if you fail to do so, you share in his guilt.
From the intensive form “thou shalt surely rebuke” [with the verb being repeated in the original Hebrew], the Rabbis deduce that the obligation to reprove sinners is to be carried out over and over again until the sinner repents, unless the sinner becomes aggressive and resorts to violence. Rabbis and preachers, especially, were called upon to offer constant rebuke to their people, although Hasidism was unhappy about the severe castigations indulged in by the preachers.
The Rabbis were realistic enough to appreciate that a rebuke can all too easily encourage defiance, hence the rabbinic saying: “Just as it is meritorious to offer reproof when it is known that it will be heeded, it is meritorious not to rebuke when it is known it will not be heeded” (Babylonian Talmud, Yevamot 65b). In this connection the verse is quoted: “Reprove not a scorner lest he hate thee; reprove a wise man and he will-love thee” (Proverbs 9: 8). It cannot be denied that conscience-counselors abounded in Jewish communities—prigs and busybodies who were only too ready to demonstrate their superiority by adopting a holier-than-thou attitude. This is probably why, even in talmudic times, one Rabbi could say (Babylonian Talmud, Arakhin16b): “I doubt whether anyone in this generation is worthy to offer rebuke.”