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

What was narrated by Muhammad bin Ahmad bin Yahya, from Ahmad bin Muhammad, from his father, from Ibn Abi Umayr, from Hammad bin ‘Uthman, from ‘Ubaydallah al-Halabi, who said: I asked Him عليه السلام about a man who, in a two-rak‘ah recommended prayer (‘nafilah’), forgot and did not sit between the two rak‘ahs, and then stood and performed the ‘ruku’ in the third. Imam عليه السلام said: "He should abandon that rak‘ah, sit down, recite the ‘tashahhud’, and give the ‘taslim’. Then he may begin a new prayer afterward."