Musnad Ahmad 27:1096

Muhammad ibn al-Hasan ibn Atash narrated to us, Ja'far ibn Sulayman narrated to us, from Hisham ibn Hassan, from Ibn Sirin, from Ibn Umar, who said: Umar ibn al-Khattab, may Allah be pleased with him, went out intending to see the Prophet, may Allah bless him and grant him peace. He came upon Utarid, a man from the tribe of Banu Tamim, who was displaying a garment of silk, selling it. Umar came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, I saw Utarid selling his garment; buy it so that you may wear it when the delegations of people come to you." He said: "Indeed, only he who has no share [in the Hereafter] wears silk."