Sahih Bukhari Volume 1, Book 8, Hadith Number 432
Narated By Sahl bin Sa’d : Allah’s Apostle went to Fatima’s house but did not find ‘Ali there. So he asked, “Where is your cousin?” She replied, “There was something between us and he got angry with me and went out. He did not sleep (mid-day nap) in the house.” Allah’s Apostle asked a person to look for him. That person came and said, “O Allah’s Apostle! He (Ali) is sleeping in the mosque.” Allah’s Apostle went there and ‘Ali was lying. His upper body cover had fallen down to one side of his body and he was covered with dust. Allah’s Apostle started cleaning the dust from him saying: “Get up! O Aba Turab. Get up! O Aba Turab (literally means: O father of dust).