The Prophet ﷺ saw a young boy whose head had been partly shaved with some hair left on it. He forbade this and said, "Shave it all or leave it all."
حدثنا عبد الرزاق حدثنا معمر عن أيوب عن نافع
أن النبي ﷺ رأى صبيا قد حلق بعض شعره وترك بعضه فنهى عن ذلك وقال احلقوا كله أو اتركوا كله
Its isnad is sahih. Abu Dawud narrated it, 4:134, from Ahmad bin Hanbal with this isnad. Munziri said, Nasai also narrated it. Muslim narrated it with the same isnad that Abu Dawud used for it, but did not mention its wording. Abu Masud Dimashqi mentioned that Muslim narrated it with this wording.I say, it is not found in Muslim with this wording. Rather, he narrated the hadith prohibiting qaza, which has passed several times, the last being 5550. Then, among his isnads, he narrated by way of Abdul-Razzaq, from Mamar, from Ayub, from Nafi, from Ibn Umar, from the Prophet, to that effect. So it is possible that this is the same wording found here, and it is possible that it follows the other wording concerning the prohibition of qaza, since the meaning is close.