Musnad Ahmad 937:64

Muhammad ibn Ubayd narrated to us, al-A’mash narrated to us, from Ibrahim al-Taymi, from his father, from Abu Dharr, who said: I was with the Messenger of Allah, peace and blessings of Allah be upon him, in the mosque when the sun set. He said: "O Abu Dharr, do you know where the sun goes?" I said: "Allah and His Messenger know best." He said: "It goes until it prostrates before its Lord, and it asks permission to return, and it is permitted. It is as if it has been told: 'Return from where you came.' So it returns to its rising place, and that is its resting place." Then he recited: {And the sun runs to a resting place for it} [Ya-Sin: 38].