Abu Dawud Book 1, Hadith Number 188.
Chapter : The performing of ablution is not essential when one takes something cooked with the help of fire.
Narated By Al-Mughirah ibn Shu’bah : One night I became the guest of the Prophet (PBUH). He ordered that a piece of mutton be roasted, and it was roasted. He then took a knife and began to cut the meat with it for me. In the meantime Bilal came and called him for prayer. He threw the knife and said: What happened! may his hands be smeared with earth! He then stood for offering prayer.
Al-Anbari added: My moustaches became lengthy. He trimmed them by placing a took-stick; or he said: I shall trim your moustaches by placing the tooth-stick there.