The Prophet (sal Allaahu alayhi wa sallam) as saying : When a dog licks a (thing contained in a) utensil you must wash it seven times, using earth (sand) for the seventh time. Abu Dawud said : This tradition has been transmitted by another chain of narrators in which there is no mention of earth. (Using translation from Abū Dāʾūd 73)
"إِذَا وَلَغَ الكلبُ في الإِناءِ فاغسلوه سبْعَ مرَّاتِ، السَّابعةُ بالتُّرابِ".