Sahih Bukhari Volume 5, Book 59, Hadith Number 640.

Narrated By Ibn Umar : The Prophet assumed the state of Ihram for Umra and Hajj, and we to assumed it for Hajj with him. When we arrived at Mecca, the Prophet said, “Whoever does not possess a Hadi should regard his Ihram for Umra only.” The Prophet had a Hadi with him. ‘Ali bin Abi Talib came to us from Yemen with the intention of performing Hajj. The Prophet said (to him), “With what intention have you assumed the Ihram, for your wife is with us?” ‘Ali said, “I assumed the lhram with the same intention as that of the Prophet.” The Prophet said, “Keep on the state of lhram, as we have got the Hadi.”