Sahih Muslim Book - 43, Hadith - 6062

حَدَّثَنَا مَنْصُورُ بْنُ أَبِي مُزَاحِمٍ ، وَمُحَمَّدُ بْنُ جَعْفَرِ بْنِ زِيَادٍ ، قَالَ مَنْصُورٌ : حَدَّثَنَا ، وقَالَ ابْنُ جَعْفَرٍ ، أَخْبَرَنَا إِبْرَاهِيمُ يَعْنِيَانِ ابْنَ سَعْدٍ ، عَنِ ابْنِ شِهَابٍ ، عَنْ عُبَيْدِ اللهِ بْنِ عَبْدِ اللهِ ، عَنِ ابْنِ عَبَّاسٍ ، قَالَ : كَانَ أَهْلُ الْكِتَابِ يَسْدِلُونَ أَشْعَارَهُمْ ، وَكَانَ الْمُشْرِكُونَ يَفْرُقُونَ رُؤُوسَهُمْ ، وَكَانَ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُحِبُّ مُوَافَقَةَ أَهْلِ الْكِتَابِ فِيمَا لَمْ يُؤْمَرْ بِهِ ، فَسَدَلَ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ نَاصِيَتَهُ ، ثُمَّ فَرَقَ بَعْدُ.

It was narrated that Ibn ‘Abbas said: “The Prophet of the Book used to let their hair fall over their foreheads and the idolaters used to part their hair. The Messenger of Allah (s.a.w) liked to do the same as the People of the Book in matters concerning which he had received no command. So the Messenger of Allah (s.a.w) let his hair fall over his forehead, then later on he parted it.”