Sunan an-Nasa'i, Book 48, Hadith 8 (In-Book) ⓘ
It was narrated that Zaid bin Al-Arqam said: "I heard the Messenger of Allah [SAW] say: 'Whoever does not take from his mustache, he is not one of us.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا الْمُعْتَمِرُ، قَالَ سَمِعْتُ يُوسُفَ بْنَ صُهَيْبٍ، يُحَدِّثُ عَنْ حَبِيبِ بْنِ يَسَارٍ، عَنْ زَيْدِ بْنِ أَرْقَمَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " مَنْ لَمْ يَأْخُذْ شَارِبَهُ فَلَيْسَ مِنَّا " .
also referenced under: Hadith 5047 (Reference) & Volume 6, Book 48, Hadith 5050 (DarusSalam)