If one brings merit to the many, sin does not come by his hand, [so that he not be in Gehinnom and his disciples in Gan Eden]; and if one causes the many to sin, he is not given the opportunity to repent, [so that he not be in Gan Eden and his disciples in Gehinnom.] Moses was meritorious and brought merit to the many [(He taught Torah to all of Israel)] — the merit of the many is attributed to him, as it is written (Deuteronomy 33:21): "He did the righteousness of the L rd and [he did] His judgments with Israel" [i.e., "His judgments that are with Israel" — it is as if he (Moses) did them.] Yeravam sinned and he caused the many to sin — the sin of the many is attributed to him, as it is written (I Kings 15:30): "For the sins of Yeravam, that he committed and that he caused Israel to commit." [Its not being written "for the sins of Yaravam and Israel" implies that all is attributed to Yeravam.]
Duties of the Heart
Likewise, my brother, if one rectifies only himself, he will have a small merit. But if one rectifies himself and many other people, he will have his merit multiplied according to the merits of all the people who he rectified to G-d, as our sages said: "Whoever brings merit to the masses will not come to any sin" (Avot 5:18), and they said: "Moshe was righteous and caused the multitude to become righteous, the merit of the multitudes is attributed to him, as written 'he performed the righteousness of G-d and His judgments with Israel", and the wise man said: "But to them that rebuke shall be delight, and a good blessing shall come upon them" (Mishlei 24:25), and "The law of truth was in his mouth - and turned many away from iniquity" (Malachi 2:6), and "those who bring merit to the multitudes will be like the stars forever and ever" (Daniel 12:3).
11. One for who repentance will be extremely hard for him: he who enticed people with a false religion that he invented and influenced them to believe in it. He sinned and caused others to sin, the more people join his false beliefs, the more his sin will increase and be multiplied over, as the sages said: "Whoever leads the masses in the right path will not come to any sin, but whoever leads the masses astray will not be able to repent for all the wrong he commits.. Yeravam ben Nevat, sinned and caused the multitude to sin, and so the sin of the masses is ascribed to him as it is written (I Kings 15:30) 'Because of the sins of Yeravam that he committed and that he caused Israel to commit.' " (Avos 5:18)