Commentary for Genesis 37:28

ויעברו אנשים מדינים AND THERE PASSED BY MIDIANITES — This was another caravan: Scripture indicates that he was sold several times.

ויעברו אנשים מדינים, while the brothers had been sitting down to consume their meal, having distanced themselves somewhat from the pit into which they had thrown Joseph in order not to be guilty of “eating while spilling blood,” they were waiting for the Ishmaelites whom they had seen in the distance, to arrive. During this period the Midianites, coming from a different direction had passed there, saw Joseph in the pit, pulled him up, and proceeded to sell him to the Ishmaelites. One may assume that the brothers had no knowledge of this. Even though the Torah appears to attribute the sale of Joseph to the Ishmaelites to the brothers, (based on Joseph accusing them of having sold him to Egypt, 45,4) we would have to say that because of their having been instrumental in bringing about that sale they are considered as if having assisted in that sale. This appears to me the deeper meaning of the plain meaning of the text both here and in chapter 45. The line describing the Midianites passing that way is described as something totally coincidental, having nothing to do with what the brothers had planned to do with Joseph. Even if the Torah says:וימכרו (את) יוסף לישמעאלים, this sounds as if the brothers did the selling. It is also possible that the brothers noting the Midianites suddenly materialising out of nowhere, instructed them to pull Joseph out of the pit after which they themselves sold him to the Ishmaelites.

מדינים סוחרים, the owners of the merchandise being transported on the Ishmaelites’ camels.