Sahih Bukhari Volume 1, Book 3, Hadith Number 84

Narated By Ibn ‘Abbas : Somebody said to the Prophet (during his last Hajj), “I did the slaughtering before doing the Rami.’ The Prophet beckoned with his hand and said, “There is no harm in that.” Then another person said. “I got my head shaved before offering the sacrifice.” The Prophet beckoned with his hand saying, “There is no harm in that.”