Musnad Abu Ya'la al-Mawsili 110:145

Abu Khaythama narrated to us, Hushaym narrated to us, Mansur narrated to us, from 'Ata', from Ibn 'Abbas, that the Prophet (may Allah bless him and grant him peace) was asked about someone who shaved before he slaughtered, and the like of that, and he would say: "No harm, no harm."