The Messenger of Allah ﷺ forbade qazaa, which is to shave part of a child's head and leave some of the hair.
حدثنا أحمد بن حنبل حدثنا عثمان بن عثمان قال أحمد كان رجلا صالحا قال أخبرنا عمر بن نافع عن أبيه
نهى رسول الله ﷺ عن القزع والقزع أن يحلق رأس الصبي فيترك بعض شعره
Narrated by Muslim, Libas, chapter on the dislike of qaza, no. 2120, from the hadith of Uthman, and by Bukhari, Libas, chapter on qaza, no. 5920, from the hadith of Umar bin Nafi through it. It is also found in Musnad Ahmad, 4/2, 39.