Sahih Bukhari Volume 3, Book 34, Hadith Number 272.

Narated By ‘Abbas bin Tamim : That his uncle said: “The Prophet was asked: If a person feels something during his prayer; should one interrupt his prayer?” The Prophet said: No! You should not give it up unless you hear a sound or smell something.” Narrated Ibn Abi Hafsa: Az-Zuhri said, “There is no need of repeating ablution unless you detect a smell or hear a sound.”