"The Messenger of Allah (ﷺ) said: 'If one of you is not sure about his prayer, let him estimate and prostrate twice after he has finished."
Sunan an-Nasa'i Book 13, Hadith 63
← Previous Hadith "If one of you is not sure about his prayer, let him estimate what he thinks is most likely to be correct and complete the prayer on that basis, then let him prostrate twice."

Sunan an-Nasa'i Book 13, Hadith 62 Next Hadith → "The Messenger of Allah (ﷺ) prayed and did more or less (rak'ahs). When he had said the taslim, it was said: 'O Messenger of Allah, has there been some change concerning the prayer?' He said: 'If there had been some change concerning the prayer, I would have told you. Rather I am a human being and I forget as you forget. If any one of you is not sure about his prayer, let him consider an estimate of what is correct, and complete his prayer on that basis, then say the taslim and prostrate twice.'"

Sunan an-Nasa'i Book 13, Hadith 64