פירוש על דברי הימים ב 21:8

In his days, Edom rebelled, etc. For David had destroyed all the males in Edom, and he appointed governors over them instead of a king, and they paid him tribute, and all the kings of Judah did similarly: they appointed governors who pleased them. And from the days of Joram and thereafter, they [the Edomites] rebelled against the authority of Judah.