The Prophet (ﷺ) prostrated after the salam when he was not sure.
Sunan an-Nasa'i Book 13, Hadith 57
← Previous Hadith A similar report was narrated from Abu Hurairah from the Messenger of Allah (ﷺ).

Sunan an-Nasa'i Book 13, Hadith 56 Next Hadith → The Prophet (ﷺ) led them in prayer and forgot (how many rak'ahs he had prayed), then he prostrated twice, then he said the salam.

Sunan an-Nasa'i Book 13, Hadith 58