Chapter on Rulings on Forgetfulness (Sahw) in Prayer and What Requires Repeating of Prayer

What was narrated by Muhammad bin Ya‘qub, from Ali bin Ibrahim, from his father, and from Muhammad bin Isma‘il, from al-Fadl bin Shadhan, all from Hammad bin ‘Isa, from Hariz, from Zurarah and Abu Basir, who said: We said to Him عليه السلام: “A man frequently doubts in his prayer to the extent that he no longer knows how much he has prayed or what remains upon him.” Imam عليه السلام said: "He should repeat (the prayer)." We asked: “But it happens to him frequently, every time he repeats, he doubts again.” Imam عليه السلام said: "Then he should proceed with his doubt." Then Imam عليه السلام said: "Do not accustom the evil one (‘al-khabith’), meaning the Shaytan, from yourselves to breaking the prayer, lest you encourage him, for Shaytan is wicked and becomes accustomed to whatever he is trained with. So let one of you proceed in his assumption and not frequently invalidate the prayer, for if he does that repeatedly, the doubt will not return to him." Zurarah said: “Then Imam عليه السلام said: ‘Indeed, the evil one only wants to be obeyed; so when he is disobeyed, he does not return to any one of you.’"