Abu Dawud Book 1, Hadith Number 153.
Chapter : Wiping over the shoes.
Narated By N/A : Abu ‘Abd al-Rahman al-Sulami said that he witnessed ‘Abd al-Rahman b. ‘Awf asking Bilal about the ablution of the Prophet (may peace be upon him). Bull said: He went out to relieve himself. Then I brought water for him and he performed ablution, and wiped over his turban and socks.