Sunan Ibn Majah 1209

Abu Yusuf Ar-Raqqi Muhammad bin Ahmad As-Saidalani narrated to us: Muhammad bin Salamah narrated to us, from Muhammad bin Ishaq, from Makhul, from Kuraib, from Ibn Abbas, from Abdur-Rahman bin Awf, who said: I heard the Messenger of Allah (ﷺ) say: If one of you is uncertain whether he has prayed two or one rakah, let him count it as one. If he is uncertain whether he has prayed two or three, let him count it as two. If he is uncertain whether he has prayed three or four, let him count it as three. Then let him complete what remains of his prayer so that the uncertainty concerns the additional amount, then let him perform two prostrations while seated before giving the taslim.