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

As for what was narrated by Muhammad bin Ahmad bin Yahya, from Ahmad bin al-Hasan bin Ali bin Faddal, from ‘Amr bin Sa‘id al-Mada’ini, from Musaddiq bin Sadaqah, from ‘Ammar bin Musa al-Sabati: Abu Abdillah عليه السلام (was asked) regarding a man who forgot the ‘tashahhud’ in prayer. Imam عليه السلام said: "If he remembers that he at least said ‘Bismillah’, then his prayer is valid. But if he does not remember anything from ‘tashahhud’, he must repeat prayer." And (Imam عليه السلام was asked) regarding a man who remembers after having stood up, spoken, and gone about his affairs, that he had only prayed two rak‘ahs in Dhuhr, ‘Asr, Isha, or Maghrib. Imam عليه السلام said: "He builds upon his prayer and completes it, even if he had reached China, and he does not need to repeat the prayer."