Commercial Transactions (Kitab Al-Buyu)
Dawud :: Book 22 : Hadith 3348
Narrated Abdullah ibn Umar:
I used to sell camels at al-Baqi for dinars and take dirhams for them, and sell for dirhams and take dinars for them. I would take these for these and give these for these. I went to the Apostle of Allah (peace_be_upon_him) who was in the house of Hafsah. I said: Apostle of Allah , take it easy, I shall ask you (a question): I sell camels at al-Baqi'. I sell (them) for dinars and take dirhams and I sell for dirhams and take dinars. I take these for these, and give these for these. The Apostle of Allah (peace_be_upon_him) then said: There is no harm in taking them at the current rate so long as you do not separate leaving something to be settled.