صَحِيحُ مُسْلِمٍ
Sahih Muslim 1301 d
The Book of Pilgrimage
Shaving the head is preferrable to cutting the hair, although cutting the hair is permissible
وَحَدَّثَنَاهُ ابْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، حَدَّثَنَا عُبَيْدُ اللَّهِ، بِهَذَا الإِسْنَادِ وَقَالَ فِي الْحَدِيثِ فَلَمَّا كَانَتِ الرَّابِعَةُ قَالَ وَالْمُقَصِّرِينَ .
Ubaidullah reported this hadith with the same chain of transmitters and (it is said) that it was on the fourth turn that he (the Prophet) said: (May Allah have mercy upon) those who got their hair clipped."
Sahih Muslim, 1301 dSahihصحيح