John Calvin Commentary Genesis 37:28

"And there passed by Midianites, merchantmen; and they drew and lifted up Joseph out of the pit, and sold Joseph to the Ishmaelites for twenty pieces of silver. And they brought Joseph into Egypt." — Genesis 37:28 (ASV)

Then there passed by Midianites. Some think that Joseph was sold twice in the same place. For it is certain, since Midian was the son of Abraham and Keturah, that his sons were distinct from the sons of Ishmael; and Moses has not recorded these different names carelessly. But I interpret the passage this way: Joseph was offered for sale to anyone willing to buy, and because his purchase was declined by the Midianites, he was sold to the Ishmaelites.

Moreover, though they might justly suspect the sellers of having stolen him, yet the desire for gain prevents them from inquiring. We may also add what is probable: that on the journey, they asked who Joseph was. But they did not value their common origin enough to prevent them from eagerly seeking profit.

This passage, however, teaches us to what extent the sons of Abraham according to the flesh were preferred over the elect offspring, in which, nevertheless, the hope of the future Church was included.

We see that from the two sons of Abraham such a great posterity was propagated that merchants came from both in various places, while that part of his seed which the Lord had chosen for Himself was still small. Thus, the children of this world, like premature fruit, quickly achieve the greatest wealth and the height of happiness; whereas the Church, progressing slowly through the greatest difficulties, scarcely attains, during a long period, even a moderate condition.