It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Magians were mentioned before the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "They let their moustaches grow long and shave their beards, so oppose them." So Sayyiduna Ibn Umar (may Allah be pleased with them both) would examine his moustache and clip it just as a sheep's wool is sheared.
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Maymun (may Allah have mercy on him) except Ma'qil (may Allah have mercy on him)."
Hadith Referenceالمعجم الأوسط / باب الألف / 1622
Hadith Takhrij«أخرجه ابن حبان فى «صحيحه» برقم: 5476، والبيهقي فى «السنن الكبرى» برقم: 707، والطبراني فى «الكبير» برقم: 14140، والطبراني فى «الأوسط» برقم: 1051»