Sunan an-Nasa'i 1240
سنن النسائي#1240SahihIt was narrated from 'Abdullah and attributed to the Prophet (ﷺ):"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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 13:62