Qatada قتادة · Commercial Transactions (Kitab Al-Buyu)

The Messenger of Allah (ﷺ) as saying: Gold for gold is interest unless both hand over on the spot ; wheat for wheat is interest unless both hand over on the spot ; dates for dates is interest unless both hand over on the spot ; barley for barley is interest unless both hand over on the spot.

The tradition mentioned above has also been transmitted by Simak (b. Harb) with a different chain of narrators and to the same effect. The first version is more perfect. It does not mention the words "at the current rate".