Sayyiduna Abu Umamah al-Bahili (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) came out to some elders of the Ansar whose beards were white, and said: "O assembly of the Ansar! Dye your hair red or yellow, and differ from the People of the Book."
We said: O Messenger of Allah! The People of the Book do not wear leather socks or sandals. He said: "Wear leather socks and sandals, and differ from the People of the Book."
We said: O Messenger of Allah! The People of the Book trim the hair of their chins and grow their moustaches long. The Messenger of Allah (peace and blessings be upon him) said: "Trim your moustaches and let your beards grow."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7893