Concession for Shaving the Head

It was narrated from Ibn 'Umar that :

The Prophet ﷺ saw a boy, part of whose head had been shaven and part had been left. He forbade that and said: "Shave all of it, or leave all of it."

أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَنْبَأَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَنْبَأَنَا مَعْمَرٌ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ ﷺ رَأَى صَبِيًّا حَلَقَ بَعْضَ رَأْسِهِ وَتَرَكَ بَعْضَ فَنَهَى عَنْ ذَلِكَ وَقَالَ " احْلِقُوهُ كُلَّهُ أَوِ اتْرُكُوهُ كُلَّهُ " .