From him, from Fadala ibn Ayyub, from Musa ibn Bakr, from Zurarah, from Abu Ja’far عليه السلام, peace be upon him, who said: Imam al-Baqir عليه السلام said: “If a man forgets a prayer or performs it without purification (tahur), while he is residing or traveling, then remembers it. He must make up what was obligatory upon him, he should neither increase upon that nor decrease. Whoever forgets four (units) must make up four (units), whether he was traveling or residing. And if he forgets two (units), he should perform two (units) when he remembers, whether he was traveling or residing.”