Musnad Ahmad 31:488

Yazid ibn Harun narrated to us, Hisham informed us, from Yahya, Iyad narrated to us that he asked Abu Sa'id al-Khudri, and he said: "One of us prays and does not know how much he has prayed?" He said: The Messenger of Allah (ﷺ) said: "If one of you prays and does not know how much he has prayed, let him prostrate two prostrations while he is sitting. And if Satan comes to one of you and says: 'You have broken your ablution during your prayer,' let him say: 'You have lied,' unless he finds a smell with his nose or hears a sound with his ear."