Performing sajda al-sahw on the basis of a supposition

Question

If in the last rak‘a of witr (while in the tashahhud) Zayd formed a predominant supposition that he had not recited the qunut supplication, and after the tashahhud Zayd gave the salam and went into prostration with the intention of sajda al-sahw, but had only just reached the first prostration when he suddenly became certain that he had recited the qunut supplication, [yet] he completed the sajda al-sahw and after that completed his prayer — was Zayd’s prayer valid or not? Please write in detail.

Answer

The prayer was valid. At the very most, what happened here is that a salam, two prostrations and one sitting (qa‘da) were performed in excess of the witr. So it will be said that when he gave the salam for sajda al-sahw, that very salam was like a salam that terminates the prayer, and with it the witr prayer had ended; whatever he did after that he did outside the prayer, and…

Source: Fatawa Mahmudiyya

Preview. The full text opens with JavaScript enabled.