(25) باب التَّحَرِّي
It was narrated that 'Abdullah said:
"Whoever has doubt, or is not sure, let him estimate what is correct, then let him prostrate twice." (RU)
Reference (RU): Sunan an-Nasa'i 1246 (RU)
In-book reference (RU): Book 13, Hadith 68 (RU)
English translation (RU): Vol. 2, Book 13, Hadith 1247 (RU)