Musannaf Ibn Abi Shayba 13:2546

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Simak, from Sa'id ibn Jubayr, from Ibn 'Umar, who said: I used to sell gold for silver and silver for gold. So I came to the Prophet, peace and blessings of Allah be upon him, and asked him. He said: "When you trade with your companion, do not depart from him while there is still confusion between you and him."