Sahih Bukhari | Volume 9 | Hadith Number 520

Narrated by Abu Dharr
I entered the mosque while Allah's Apostle was sitting there. When the sun had set, the Prophet said, "O Abu Dharr! Do you know where this (sun) goes?" I said, "Allah and His Apostle know best." He said, "It goes and asks permission to prostrate, and it is allowed, and (one day) it, as if being ordered to return whence it came, then it will rise from the west." Then the Prophet recited, "That: "And the sun runs on its fixed course (for a term decreed)," (36:38) as it is recited by 'Abdullah.