The Messenger of Allah ﷺ forbade qaza'. Qaza' means having part of a boy's head shaved and leaving part unshaven. (Using translation from Abū Dāʾūd 4193)
نَهَى رَسُولُ اللهِ ﷺ عَنِ الْقَزَعِ وَالْقَزَعُ أَنْ يُحْلَقَ رَأْسُ الصَّبِيِّ وَيُتْرَكَ بَعْضُ شَعَرِهِ