Sunan an-Nasa'i 5228
سنن النسائي#5228Sahihأَخْبَرَنَا أَحْمَدُ بْنُ عَبْدَةَ، قَالَ أَنْبَأَنَا حَمَّادٌ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم نَهَى عَنِ الْقَزَعِ .
It was narrated from Ibn 'Umar that:The Prophet [SAW] forbade Al-Qaza' (shaving part of the head and leaving part)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 48:189