Al-Kāfi

7. Muhammad ibn Yahya has narrated the following: “Muhammad ibn al-Hassan once wrote to abu Muhammad (a.s.), that a man has sworn to disown Allah and the Messenger of Allah, O Allah, grant compensation to Muhammad and his family worthy of their services to Your cause, and he then opposed his oath and about what is his repentance and expiation. He (the Imam) (a.s.), signed the answer that said, ‘He must feed ten destitute people with one mud (a certain measurement) to each one and ask forgiveness from Allah, most Majestic, most Glorious.’”