Chapter on the Detailed Explanation of Prayer, Including the Obligatory and Recommended, and What is Permissible and Not Permissible.

Al-Husayn ibn Sa‘id, from Safwan ibn Yahya, from al-Husayn ibn Abi al-‘Ala, who said: I asked Abu Abdillah عليه السلام, peace be upon him, about a man who performs two rak‘ahs of the obligatory prayer and does not sit until he bows in the third (rak‘ah). Imam عليه السلام said: "He should complete his prayer, then give the salam, and perform the two prostrations of forgetfulness (sajdatay al-sahw) while he is seated, before he speaks."