Sahih al-Bukhari · Book 25 · Hadith 1721
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ حَوْشَبٍ، حَدَّثَنَا هُشَيْمٌ، أَخْبَرَنَا مَنْصُورٌ، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ سُئِلَ النَّبِيُّ صلى الله عليه وسلم عَمَّنْ حَلَقَ قَبْلَ أَنْ يَذْبَحَ وَنَحْوِهِ. فَقَالَ " لاَ حَرَجَ، لاَ حَرَجَ ".
Narrated Ibn `Abbas: The Prophet (ﷺ) was asked about a person who had his head shaved before slaughtering (his Hadi) (or other similar ceremonies of Hajj). He replied, "There is no harm, there is no harm."
Sahih