Adam Clarke on 2 Kings 8:21

Joram went over to Zair - This is the same as Seir, a chief city of Idumea. So Isa 21:11 : The burden of Dumah (Idumea). He calleth to me out of Seir.

Smote the Edomites - It appears that the Israelites were surrounded by the Idumeans; and that in the night Joram and his men cut their way through them, and so got every man to his tent, for they were not able to make any farther head against these enemies; and therefore it is said, that Edom revolted from under the hand of Judah unto this day.