Allah's Messenger (ﷺ) 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 (midday nap) in the house." Allah's Messenger (ﷺ) asked a person to look for him. That person
came and said, "O Allah's Messenger (ﷺ)! He (Ali) is sleeping in the mosque." Allah's Messenger (ﷺ) 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 Messenger (ﷺ) started cleaning the dust from him saying: "Get up! O Aba Turab. Get up!
O Aba Turab (literally means: O father of dust).
Sahih al-Bukhari Book 8, Hadith 90