Musnad Ahmad 2:42

'Abd al-Samad narrated to us, my father narrated to me, Yazid—meaning al-Rishk—narrated to us, from Mu'adhah, from Umm 'Amr bint 'Abd Allah, that she heard 'Abd Allah ibn al-Zubayr saying: I heard 'Umar ibn al-Khattab saying in his sermon that he heard the Messenger of Allah (may Allah bless him and grant him peace) saying: "Whoever wears silk in the world shall not be clothed in it in the Hereafter."