Muhammad bin Ahmad bin Yahya, from Muhammad bin al-Husayn, from Muhammad bin Abdillah bin Hilal, from ‘Uqbah bin Khalid: Abu Abdillah عليه السلام, peace be upon him, said regarding a man who prayed the Night Prayer and performed the ‘Witr’, then remembered that he had forgotten two rak‘ahs from his prayer, what should he do? Imam عليه السلام said: "He should stand and pray the two rak‘ahs that he forgot at that place, then perform the ‘Witr’ again."