Hazrat Mak'hool narrates that the Messenger of Allah, peace and blessings be upon him, said: If any of you has doubt about his prayer as to how many rak'ahs he has performed, and if he is uncertain whether it was one or two rak'ahs, then he should perform one more rak'ah so that the doubt turns into excess. Then, while sitting in the position of Tashahhud, before saying the final salam, he should perform Sajdah Sahw, and then say the salam. Hazrat Kareeb says that regarding this hadith, Hazrat Umar and Hazrat Ibn Abbas, may Allah be pleased with them both, had a difference of opinion, so Hazrat Abdur Rahman bin Auf came and informed them that he had heard this hadith from the Messenger of Allah, peace and blessings be upon him.