Sahih Bukhari Volume 5, Book 59, Hadith Number 680.

Narrated By Abu Musa Al-Ashari : I came to the Prophet at a place called Al-Batha’. The Prophet said, “Did you assume the Ihram for Hajj?” I said, “Yes,” He said, “How did you express your intention (for performing Hajj)? ” I said, “Labbaik (i.e. I am ready) to assume the Ihram with the same intention as that of Allah’s Apostle.” The Prophet said, “Perform the Tawaf around the Ka’ba and between Safa and Marwa, and then finish your Ihram.” So I performed the Tawaf around the Ka’ba and between Safa and Marwa and then I came to a woman from the tribe of Qais who removed the lice from my head.