Sahih Bukhari
Sahih Bukhari Volume 001, Book 004, Hadith Number 139.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 04. Ablutions (Wudu')
Narated By 'Abbas bin Tamim : My uncle asked Allah's Apostle about a person who imagined to have passed wind during the prayer. Allah' Apostle replied: "He should not leave his prayers unless he hears sound or smells something."