(25) باب التَّحَرِّي
It was narrated that Ibrahim said:
"They used to say: 'If one is not sure of what he estimates is correct, then prostrate twice.'" (JA)
Reference (JA): Sunan an-Nasa'i 1247 (JA)
In-book reference (JA): Book 13, Hadith 69 (JA)
English translation (JA): Vol. 2, Book 13, Hadith 1248 (JA)