Musnad Ahmad 25:1177

'Affan narrated to us, Wuhayb narrated to us, 'Abdullah ibn 'Uthman ibn Khuthaym narrated to us, from Sa'id ibn Jubayr, from Ibn 'Abbas: That a man came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, I shaved before I slaughtered?" He said: "There is no harm, so slaughter." And another came to him and said: "O Messenger of Allah, I slaughtered before I threw the pebbles?" He said: "So throw the pebbles, and there is no harm."