Selling good barley for lower-quality barley with a difference in weight

Question:
Honorable Shaykh, may Allah preserve you, is it valid to sell barley of excellent quality for barley of lower quality, with a difference in weight, if the two parties agree?

Answer:
This is not permissible. We have said that it is not permissible to make a difference in the same type based on quality or poor quality, ever. The method is to sell the poor quality for dirhams and buy some of the good quality with dirhams. As for giving a large quantity of the poor quality and taking a small quantity of the good quality of the same type, this is riba (usury or interest). This is riba.