The Book of Pilgrimage
15/55. Chapter:
Shaving the head is preferrable to cutting the hair, although cutting the hair is permissible
Sahih Muslim
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، وَأَبُو دَاوُدَ الطَّيَالِسِيُّ عَنْ شُعْبَةَ، عَنْ يَحْيَى بْنِ الْحُصَيْنِ، عَنْ جَدَّتِهِ، أَنَّهَا سَمِعَتِ النَّبِيَّ صلى الله عليه وسلم فِي حَجَّةِ الْوَدَاعِ دَعَا لِلْمُحَلِّقِينَ ثَلاَثًا وَلِلْمُقَصِّرِينَ مَرَّةً . وَلَمْ يَقُلْ وَكِيعٌ فِي حَجَّةِ الْوَدَاعِ .
Yahya b. al-Husain reported on the authority of his grandfather that Allah's Apostle (ﷺ) invoked blessing on the occasion of the Farewell Pilgrimage three times for those who got their heads shaved and once for those who got their hair clipped. In the narration transmitted by Waki' there is no mention of the Farewell Pilgrimage.
Reference : Sahih Muslim 1303In-book reference : Book 15, Hadith 354USC-MSA web (English) reference : Book 7, Hadith 2989