Sahih Al Bukhari Hadith Number 1723

Narrated Ibn `Abbas: The Prophet (peace be upon him) was asked by a man who said, “I have done the Rami in the evening.” The Prophet (peace be upon him) replied, “There is no harm in it.” Another man asked, “I had my head shaved before the slaughtering.” The Prophet (peace be upon him) replied, “There is no harm in it.”

25  Hajj (Pilgrimage)
Hadith number 1723
Volume no 2
Chapter: 125 (Slaughtering before having one’s head shaved)