Musnad Ahmad 30:329

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Abu Salih and Abu Razin, from Abu Hurairah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "If a dog laps from the vessel of one of you, let him wash it seven times. And if the sandal strap of one of you breaks, let him not walk in the other sandal until he repairs it."