Musannaf Ibn Abi Shayba 16:423

Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from Asim, from Abu Uthman, from Umar: That he used to forbid silk and brocade, except for what was like this—and he gestured with his finger, then the second, then the third, then the fourth. And he said: The Messenger of Allah, may Allah bless him and grant him peace, used to forbid us from it.