If the extra thing that a seller receives is different to what he sells – for example, he sells 1 kilogram of wheat for 1 kilogram of wheat and 10 pence – it is still usury and unlawful. In fact, even if the seller does not receive any extra goods but makes it a condition that the buyer must do something for him, it is also usury and unlawful.
Ruling 2082.* If a person gives a lesser amount but adds something else – for example, he sells 1 kilogram of wheat and one handkerchief for 1.5 kilograms of wheat – there is no problem as long as he intends the handkerchief to be the item for which he is receiving the extra amount [i.e.
the extra half kilogram of wheat,] and as long as the transaction is an immediate exchange (naqd) transaction.[2] Similarly, there is no problem if both sides add something extra – for example, one of them sells 1 kilogram of wheat and one handkerchief to the other person for 1.5 kilograms of wheat and one handkerchief – as long as they intend the handkerchief on the one side, and the handkerchief and half kilogram of wheat on the other, to be the items of exchange.