Charles Ellicott Commentary 2 Kings 8:21

"Then Joram passed over to Zair, and all his chariots with him: and he rose up by night, and smote the Edomites that compassed him about, and the captains of the chariots; and the people fled to their tents." — 2 Kings 8:21 (ASV)

So Joram went over to Zair. — No town called Zair is otherwise known. Hitzig and Ewald suggest reading Zoar, but Zoar was located in Moab, not in Edom (Jeremiah 48:34; Isaiah 15:5; Genesis 19:30; Genesis 19:37). The Vulgate has Seira, and the Arabic Sâ‘îra, which suggest an original reading, “to Seir,” the well-known mountain chain that was the headquarters of the Edomite people. Perhaps the reading of the text Çâ‘îrâh represents a dialectal pronunciation. (Compare the forms Yishâq and Yiçhâq for Isaac.)

And he rose by night. — There may be a gap of a few lines in the text here, or the compiler, in his desire to be brief, may have become obscure. Jehoram appears to have been hemmed in by the Edomites in the mountains and to have attempted escape under cover of night.

Struck the Edomites who surrounded him. — He cut his way through their ranks.

And the captains of the chariots. — This phrase is part of the object of the verb “struck.” Jehoram struck (cut his way through) the Edomites—that is, the captains of the Edomite war-chariots that hemmed him and his army in.

And the people fled into (unto) their tents. — That is, the army of Jehoram was glad to escape from the scene of its failure and made its way homeward as best it could. (Compare, for the proverbial expression, “to their tents,” 1 Samuel 20:1; 1 Kings 8:66.)

From Joel 3:19 (Edom shall be a desolate wilderness for the violence against the children of Judah, because they have shed innocent blood in their land), it has been conjectured that when the Edomites revolted, they massacred the Jews who had settled in the country during the time of their subjection. (Compare Genesis 27:40.)