Musannaf Ibn Abi Shayba 16:1042

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, from Ubayd Allah ibn Umar, from Nafi’, from Ibn Umar, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade *al-qaza’*. And *al-qaza’* is that a portion of a boy’s head is shaved and a portion is left.