Then he took his oldest son who was to reign in his place, and offered him as a burnt offering on the wall. And there came great wrath against Israel, and they departed from him and returned to their own land (2 Kings 3:27).
This is a somewhat difficult verse because it suggests that Mesha, the King of Moab, offered his first-born son, who would be next in line to the throne, as a sacrifice to his god, presumably, Chemosh, the god of the Moabites.
The difficulty is what follows. We read that "there came great wrath against Israel." Where did this wrath come from and did it come as a result of the child sacrifice?
Also, we read that "they departed from him and returned to their own land." It appears that the coalition of nations, namely, Israel, Judah, and Edom, called off the attack against Moab and went home because of this "great wrath against Israel." What are we to make of all this?
Some have suggested that the wrath was simply human indignation by the coalition at the abominable act by Mesha. They were so disturbed by this act, that they decided it was not a worthy cause to pursue.
However, others, like Keil and Delitsche, note that the vast majority of occasions for the use of the Hebrew word for "wrath" refer to God's wrath rather than human wrath or indignation. But why would God be wrathful toward Israel when Moab committed the abominable deed of child sacrifice? Keil and Delitsche conjecture that God's wrath came because the coalition "occasioned" the child sacrifice; that is, they may have induced or demanded Mesha sacrifice his first-born son, which is something strictly forbidden in the Law of Moses (Leviticus 18:21; Leviticus 20:3). But this is simply conjecture, though, if true, could explain why God was wrathful toward Israel and kept them from completely destroying the Moabites.
It would be wrong to think that Mesha's burnt offering of his son to the gods induced their god, Chemosh, to go against Israel such that the coaltion's attack was thwarted. I believe that while somewhat in the realm of conjecture, the explanation by Keil and Delitsche represents the most reasonable scenario from the text.