Sunan an-Nasa'i 1247
سنن النسائي#1247SahihIt was narrated that Ibrahim said:"They used to say: 'If one is not sure of what he estimates is correct, then prostrate twice
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih Isnaad Mauquf
Al-AlbaniSahih Isnaad Mauquf
Zubair Ali ZaiIsnaad Sahih
In-book reference: 13:69