New Defender's Study Bible Notes
37:28 Midianites. These traders are called both Midianites (here and in Genesis 37:36) and Ishmaelites (here and in Genesis 37:25). These two tribes were both descended from Abraham (he was father of both Ishmael through Hagar and Midian through Keturah), both lived in the same region, and undoubtedly both were associated closely in many ways. The result was the interchangeable use of their names.
37:28 twenty pieces of silver. Twenty pieces of silver was the going price of a slave. In the time of Zechariah (and of Christ) it was thirty pieces of silver (Zechariah 11:12-13; Matthew 26:14-15).