ENOfficial
Zaid b. Arqam reported God’s messenger as saying, “He who does not take something off his moustache is not one of us.” Ahmad, Tirmidhi and Nasa'i transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ زَيْدِ بْنِ أَرْقَمَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ لَمْ يَأْخُذ شَارِبِهِ فَلَيْسَ مِنَّا» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيُّ وَالنَّسَائِيُّ
sunnah.com