Sunan an-Nasa'i 13
سنن النسائي#13Sahihأَخْبَرَنَا 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
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 1:13