Sahih Bukhari Volume 2, Book 26, Hadith Number 773.

Narated By Anas bin Malik : The Prophet (p.b.u.h) offered four Rakat of Zuhr prayer at Medina and two Rakat of ‘Asr prayer at Dhul-Hulaifa. Narrated Aiyub: “A man said: Anas said, “Then he (the Prophet passed the night there till dawn and then he offered the morning (Fajr) prayer, and mounted his Mount and when it arrived at Al-Baida’ he assumed Ihram for both ‘Umra and Hajj.”