Shave it all or leave it all
Authentic hadithعن ابن عمر رضي الله عنهما قال: رأى رسول الله صلى الله عليه وسلم صبيًّا قد حُلِق بعض شعر رأسه وترك بعضه، فنهاهم عن ذلك، وقال: «احلقوه كله، أو اتركوه كله».
Ibn ‘Umar (may Allah be pleased with him) reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) saw a boy who had part of his head shaved and part left unshaven, so he forbade them from doing this, and said: "Shave it all or leave it all."
Explanation
The Messenger of Allah (may Allah’s peace and blessings be upon him) saw a boy who had part of his head shaved and the rest unshaven, so he forbade the adults from doing this to the boy again. He told them not to shave part of the head and leave the other part unshaven.
Source · An-Nasaa’i - Narrated by Abu Daoud
From the Hadith Encyclopedia (hadeethenc.com).