5. Ali ibn Ibrahim has narrated from his father from Hammad, from Hariz from Muhammad ibn Muslim who has said the following: “I once said to him (the Imam) عليه السلام, ‘There is a man who has become ill and has omitted optional Salah (prayer).’ He (the Imam) said, ‘O Muhammad, it is not obligatory Salah (prayer). If he performs, it is a good deed that he does. If he did not do, he is not required to perform it.’”