Musannaf Ibn Abi Shayba 13:3240

Abu Bakr narrated to us, he said: Yazid bin Harun narrated to us, from Ibn Abi Dhi'b, from al-Zuhri, from Hamzah bin Abdullah bin Umar bin al-Khattab, who said: We used to trade in garments in the presence of Abdullah bin Umar. Whoever followed, followed with a dirham, and he would neither command us nor forbid us.