Sunan Ibn Majah
3051
Sahih+3

It was narrated from ‘Abdullah bin ‘Amr that the Prophet (ﷺ) was asked about a man who slaughtered his sacrifice before shaving his head, or who shaved his head before slaughtering his sacrifice, and he said:“There is no harm in that.”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi