The Prophet ﷺ saw a boy whose head had been partly shaved while the rest of his hair was left untouched. He forbade them from doing this and said, "Shave all of it, or leave all of it."
أن النبي ﷺ رأى صبيا قد حلق بعض شعره وترك بعضه، فنهاهم عن ذلك، وقال: احلقوه كله، أو اتركوه كله
Reported by Abu Dawud (4195), Nasai (5048), and Ahmad (5615), all of them from Abdul-Razzaq, and it is in his Musannaf (19564), he said, Muammar narrated to us, from Ayub, from Nafi, from Ibn Umar, and he related it. Its isnad is sahih. Muslim also cited this isnad (2120) but did not mention its wording, instead referring to the wording mentioned before it.