The Book of Purification
2/16. Chapter:
The characteristics of the fitrah
Sahih Muslim
حَدَّثَنَا سَهْلُ بْنُ عُثْمَانَ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، عَنْ عُمَرَ بْنِ مُحَمَّدٍ، حَدَّثَنَا نَافِعٌ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " خَالِفُوا الْمُشْرِكِينَ أَحْفُوا الشَّوَارِبَ وَأَوْفُوا اللِّحَى " .
Ibn Umar said: The Messenger of Allah (may peace be opon him) said: Act against the polytheists, trim closely the moustache and grow beard.
Reference : Sahih Muslim 259cIn-book reference : Book 2, Hadith 69USC-MSA web (English) reference : Book 2, Hadith 500