Musannaf Ibn Abi Shayba 35:97

Asbat ibn Muhammad narrated to us, from al-Shaybani, from Ziyad ibn 'Alaqah, from Usamah ibn Sharik, that a man asked the Prophet, peace and blessings of Allah be upon him, and said: "I shaved before I slaughtered." He said: "There is no harm."