The Messenger of Allah ﷺ came out to a group of elderly men from the Ansar whose beards had turned white and said, "Company of the Ansar, dye them red or yellow and differ from the People of the Book."I said, "Messenger of Allah, the People of the Book wear trousers but do not wear waist-wrappers."The Messenger of Allah ﷺ replied, "Wear trousers and wear waist-wrappers, and differ from the People of the Book."I said, "Messenger of Allah, the People of the Book wear leather socks but do not wear sandals."The Prophet ﷺ said, "Wear leather socks and wear sandals, and differ from the People of the Book."We said, "Messenger of Allah, the People of the Book trim their beards and let their mustaches grow long."The Prophet ﷺ said, "Trim your mustaches and let your beards grow full, and differ from the People of the Book."
حدثنا زيد بن يحيى حدثنا عبد الله بن العلاء بن زبر حدثني القاسم قال سمعت
خرج رسول الله ﷺ على مشيخة من الأنصار بيض لحاهم فقال يا معشر الأنصار حمروا وصفروا وخالفوا أهل الكتاب قال فقلت يا رسول الله إن أهل الكتاب يتسرولون ولا يأتزرون فقال رسول الله ﷺ تسرولوا وائتزروا وخالفوا أهل الكتاب قال فقلت يا رسول الله إن أهل الكتاب يتخففون ولا ينتعلون قال فقال النبي ﷺ فتخففوا وانتعلوا وخالفوا أهل الكتاب قال فقلنا يا رسول الله إن أهل الكتاب يقصون عثانينهم ويوفرون سبالهم قال فقال النبي ﷺ قصوا سبالكم ووفروا عثانينكم وخالفوا أهل الكتاب
Its isnad is sahih. Abdullah bin Ala bin Zabr is trustworthy, and his hadith appears in Bukhari and the four Sunan compilers. This hadith has already come up many times. Haythami said in 5/131 and 160, "The men of Ahmad's narration are the men of the Sahih, except for Qasim, and there is some discussion about him that does not cause harm." His statement "Trim your sibal" means your mustaches, and "your athanin" means your beards.