Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I used to sell camels at al-Baqi'. I would sell for dinars but take dirhams in their place, and I would sell for dirhams and take dinars in their place. I came to the Messenger of Allah (peace and blessings be upon him) as he was about to enter the house of Sayyidah Hafsah (may Allah be pleased with her). I said: O Messenger of Allah (peace and blessings be upon him)! I sell camels at al-Baqi'; I sell for dinars and take dirhams in their place, and sometimes I sell for dirhams and take dinars. He (peace and blessings be upon him) said: "There is no harm, when you take it at that day's rate, as long as the two of you do not part with anything remaining between you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10695