The Messenger of Allah ﷺ said, "Whoever does not trim his moustache is not one of us."
حدثنا أحمد بن منيع حدثنا عبيدة بن حميد عن يوسف بن صهيب عن حبيب بن يسار
أن رسول الله ﷺ قال من لم يأخذ من شاربه فليس منا
[Sahih]. Nasai also recorded it (1/15, no. 13) from the hadith of Ubayda bin Humayd, transmitted the same way, and Yahya Qattan followed him in this narration. Ibn Hibban graded it sahih (al-Ihsan, no. 5453).On this subject there is also a report from Mughira bin Shuba [Abu Dawud, no. 188, and Tirmidhi in al-Shamail, no. 165].