Abu Dawud Book 1, Hadith Number 149.
Chapter : Wiping over the shoes.
Narated By Al-Mughirah b. Shu’bah : I was in the company of the Messenger of Allah (may peace be upon him) in the expedition of Tabuk. He abandoned the main road before the dawn prayer, and I also did the same along with him. The Prophet (may peace be upon him) made his camel kneel down and (went to) relieve himself. He then came back and I poured water upon his hands from the skin vessel. He then washed his hands and face. He tried to get his forearms out (of the gown), but the sleeves of the gown were too narrow, so he entered back both his hands, and brought them out from beneath the gown. He washed his forearms up to the elbows and wiped his head and wiped over his socks. He then mounted (his camel) and we began to proceed until we found people offering the prayer. They brought forward ‘Abd al-Rahman b. ‘Awf who was leading them in prayer, starting it at the proper time. He had already completed a rak’ah of the dawn prayer. The Prophet (may peace be upon him) stood in the row side by side with other Muslims. He performed the second rak’ah of the prayer behind ‘Abd al-Rahman b. ‘Awf. Then ‘Abd al–Rahman uttered salutation. The Prophet (may peace be upon him) stood to perform the remaining rak’ah of the prayer. The Muslims were alarmed. They began to utter tasbih (Subhan Allah) presuming that they had offered prayer before the Prophet (may peace be upon him) had done. When he uttered the salutation (i.e. finished his prayer), he said: You were right, or (he said) you did well.