The Prophet ﷺ saw a boy with part of his head shaved and part left unshaven. He forbade them to do that, saying: Shave it all or leave it all. (Using translation from Abū Dāʾūd 4195)  

أَنَّ رَسُولَ اللهِ ﷺ رَأَى صَبِيًّا حَلَقَ بَعْضَ شَعْرِهِ وَتَرَكَ بَعْضَهُ فَنَهَى عَنْ ذَلِكَ وَقَالَ «احْلِقُوهُ كُلَّهُ أَوِ اتْرُكُوهُ كُلَّهُ»