The Book of Purification
1/13. Chapter:
Trimming The Mustache
Sunan an-Nasai
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا عَبِيدَةُ بْنُ حُمَيْدٍ، عَنْ يُوسُفَ بْنِ صُهَيْبٍ، عَنْ حَبِيبِ بْنِ يَسَارٍ، عَنْ زَيْدِ بْنِ أَرْقَمَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ لَمْ يَأْخُذْ شَارِبَهُ فَلَيْسَ مِنَّا " .
It was narrated that Zaid bin Arqam said: "The Messenger of Allah (ﷺ) said: 'Whoever does not trim his mustache, he is not from one of us.'"
Reference : Sunan an-Nasa'i 13In-book reference : Book 1, Hadith 13English translation : Vol. 1, Book 1, Hadith 13