It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that I used to sell camels in Jannat al-Baqi'. If I sold for dinars, I would take dirhams from the buyer, and if I sold for dirhams, I would take dinars from him. One day, to find out about this issue, I came to the Prophet (peace and blessings be upon him), and at that time he was entering his chamber. I held onto his garment and asked him about this issue, so the Prophet (peace and blessings be upon him) said: "When you receive one of the two in exchange for the other, do not separate from your companion until there remains no transaction between you and him."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5555
Hadith Gradingحکم دارالسلام:إسناده ضعيف لتفرد سماك بن حرب برفعه