Sahih Muslim
The Book of Purification (Kitab Al-Taharah)
Book Number: 002 / Hadith Number: 540
Sulaiman b. Buraida narrated it from his father that the Apostle of Allah (may peace be upon him) offered prayers with one ablution on the day of the Conquest (of Mecca) and wiped over the socks. 'Umar said to him: You have today done something that you have not been accustomed to before. He (the Holy Prophet) said: 0 'Umar, I have done that on purpose.