Musnad Ahmad 27:1347

Muhammad ibn Ubayd narrated to us, Ubaydullah narrated to us, from Nafi, from Ibn Umar, that Umar saw a garment of silk (sira') being sold at the door of the mosque. He said: "O Messenger of Allah, if you were to buy it and wear it on Friday, and for the delegations when they come to you." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, only he who has no share in the Hereafter wears this." Then, garments of that type came to the Messenger of Allah (peace and blessings of Allah be upon him), and he gave one of them to Umar. Umar said: "O Messenger of Allah, you have clothed me with it, yet you said about it what you said." The Messenger of Allah (peace and blessings of Allah be upon him) said: "I did not clothe you with it so that you would wear it; I only clothed you with it so that you might sell it or give it as a garment." He said: So Umar gave it as a garment to a brother of his in Makkah who was a polytheist, from his mother's side.