Al-Husayn bin Sa‘id, from Fadalah, from al-Qasim bin Burayd, from Muhammad bin Muslim: Abu Ja‘far عليه السلام, peace be upon him, (said) regarding a man who prayed two rak‘ahs of an obligatory prayer (‘al-maktubah’), then gave the ‘taslim’ thinking that he had completed the prayer and spoke, then remembered that he had only prayed two rak‘ah. Imam عليه السلام said: "He should complete what remains of his prayer, and there is nothing upon him."