Musannaf Ibn Abi Shayba 1:1861

Waki’ narrated to us, from Sufyan, from Alqamah ibn Marthad, from Sulayman ibn Buraydah, from his father: That the Messenger of Allah (may Allah bless him and grant him peace), on the day of the conquest of Makkah, performed ablution and wiped over his leather socks. Umar said, "O Messenger of Allah (may Allah bless him and grant him peace), I saw you today do something you were not accustomed to doing before today." He said, "O Umar, I did it intentionally."