The Edomites took advantage of the reverses of Ahaz, and were perhaps in league with Rezin (see 2-Kings 16:6 note). The pitilessness of Edom, and her readiness to turn against Judah in any severe distress, is noticed and sternly rebuked by the prophets (Amos 1:11; Ezekiel 35:5; Obadiah 1:10-14, etc.).

For again the Edomites had come,.... As in the days of Jehoshaphat, 2-Chronicles 20:10,
and smitten Judah, and carried away captives; taking the advantage of the weak and low condition Ahaz was in, and which was the reason of his sending to the king of Assyria.

again the Edomites had come and smitten Judah--This invasion must have been after Rezin (at the beginning of the recent Syro-Israelitish war), had released that people from the yoke of Judah (2-Chronicles 15:11; compare 2-Kings 16:6).

2-Chronicles 28:17 is to be translated, "And besides, the Edomites had come, and had inflicted a defeat upon Judah, and carried away captives." עוד, yet besides, praeterea, as in Genesis 43:6; Isaiah 1:5. The Edomites had been made subject to the kingdom of Judah only by Amaziah and Uzziah (2-Chronicles 25:11., 2-Chronicles 26:2); but freed by Rezin from this (cf. 2-Kings 16:6), they immediately seized the opportunity to make an inroad upon Judah, and take vengeance on the inhabitants.