Ruling on buying wheat and then returning it with its like at harvest

Question:
Is it permissible for me to buy wheat from a farmer, and give him a bag like the one I took from him at harvest, or say to him: a loan, or one bag for two bags?

Answer:
This requires a detailed explanation:
As for the loan: if you take from him a bag containing one hundred sa' (a dry measure of about 3 kg), or two hundred sa' (a dry measure of about 3 kg), forty kilos, thirty kilos, by way of loan or credit; there is no harm, whether it is dates, rice, or anything else, by way of loan or credit.
As for the sale: do not buy any grain with other grain on a deferred basis, not with the like, nor with more. You say: give me a bag containing forty kilos of dates or rice for sixty kilos on a deferred basis. This is riba (usury or interest), and this is not permissible. Even if it is cash, you do not take forty kilos of good dates for sixty kilos of bad dates. This is riba (usury or interest), even if it is immediate. It must be like for like, sa' (a dry measure of about 3 kg) for sa' (a dry measure of about 3 kg), kilo for kilo. You do not increase this over that in dates, and so on for rice, and so on for wheat. However, if it is different: if you take, for example, forty kilos of wheat for fifty kilos of barley, or forty kilos of wheat for thirty kilos of different rice, hand to hand; there is no harm in that.