Abu Dawud Book 1, Hadith Number 105.

Chapter : A man who puts his hands in the utensil before washing it.

Narated By Abu Hurairah : I heard the Messenger of Allah (PBUH) say: “When any one of you wakes from sleep, he should not put his hand in the utensil until he washes it three times, for none of you knows where his hand remained during the night or where it went round.