Rebuke

We are taught that the 613 commandments of the Torah correspond to the letters in the Ten Commandments. Each commandment, in order, corresponds to another letter. Commandment 240 is the commandment to rebuke someone if you see them engaged in wrongdoing. It corresponds to the 240th letter in the Ten Commandments, the letter א (Aleph) . The Otsar HaChayim explains that this is to hint to you the root of the concept of rebuke.
One should not rebuke as a means of rejecting or putting down someone else. The Torah's concept of rebuke is that it should lead to unity, as represented by the letter א. א Which represents the word אחד (Echad-One) has the same numerical value as אהבה (Ahava-Love). This too is to remind us that rebuke must be an act born of love, not anger or hatered. When given in that manner it will lead to the unity of the א.