Ali ibn Ibrahim from his father from Hammad from Hariz from Muhammad ibn Muslim who said: I said to Imam al-Baqir عليه السلام: “A man fell ill and left the supererogatory prayer (al-nafilah).” Imam said: “O Muhammad, it is not an obligation. If he makes it up, then it is a good deed that he does, and if he does not do it, then there is nothing upon him.”