Surely the recitation of the Qur'an is an atonement for the sins, a covering (protection) from the Hell Fire, and a safety from the punishment. Mercy will descend upon the reciter, the Angels will seek forgiveness for him, Heaven will long for that person, and his Master (Allah) will be pleased with him.

Biharul Anwar, Volume 93, Page 17 - Shi'ite Hadith