Sahih Muslim 5559
صحيح مسلم#5559SahihIbn Umar reported that Allah's Messenger (ﷺ) forbade Qaza. I said to Nafi:What is Qaza'? He said: This means having a part of a boy's head shaved and leaving a part unshaven
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 37:169