How can the King of Moab sacrificing his son cause great wrath against Israel?

Answer:

II Kings 3:27 has puzzled many people, and you'll find many explanations. The difficulty is that the Hebrew text is a bit vague.

The events in II Kings 3 involve Jehoram, King of Israel, Jehoshaphat, King of Judah, and Mesha, King of Moab. What is particularly interesting is that a stele has been found where Mesha recorded his views of these events (The Mesha Stele).

Mesha and his ancestors had been subjugated by Omri (Ahab's father and Jehoram's grandfather). For many years, Moab had to make large tribute payments to Israel (II Kings 3:4). However, when Ahab died, and Jehoram had just taken the throne, Mesha decided that this was a good time to rebel. Jehoram asked Jehoshaphat to help squash this rebellion (II Kings 3:7).

via BibleMapper.com

The kings decided to lead an army against Moab by going around the south side of the Dead Sea and attaching Moab from the south. Likely, they thought Moab would not be expecting an attack from Israel from that direction. As they went, the king of Edom joined them.

However, Jehoram became nervous. He realized that none of his companions were truly allies and that he could easily be killed so far from his country (II Kings 3:10). To calm Jehoram, a prophet was sought, and Elisha was available. God, through Elisha, said He would have nothing to do with Israel since they worship idols. Jehoram took that as confirmation that God was seeking to kill off all three kings (Israel, Judah, and Edom). However, Elisha said he is only here because God recognizes Jehoshaphat. Elisha then gives Jehoshaphat an unusual battle plan. They were to fill the valley with trenches. Those trenches would miraculously fill with water to water the armies, and then they were to destroy Moab.

Early the next morning, the Moabite army saw lots of red in the valley where the opposing army was camped. The water reflected the light of dawn, but Moab assumed that the kings had fought among themselves and the armies had killed each other. So, Moab charged in to collect the spoils from the battle. But instead of dead soldiers, they found men fresh and ready for battle. The army was defeated, and the three kings charged in to destroy Moab, which was no longer well-protected.

Mesha was trapped in a city and only had 700 soldiers left to him. He attempted to break out by charging Edom's army, assuming it was the weak link, but failed. In desperation, Mesha took his eldest son, his heir to the throne, and sacrificed him on the wall of the city. Moab had long worshipped Chemosh (II Kings 11:7). The worshippers of Chemosh believed that the greater your sacrifice to Chemosh, the more likely that Chemosh would answer your request. The Mesha Stele shows that Mesha was a devoted follower of Chemosh. There was a belief among idolaters that the higher the altar, the more likely the gods would notice the sacrifice.

The problem is that Israel has been caught up in idolatry for hundreds of years. That left them superstitious. They concluded that the Moabite god directed great wrath toward them, demoralizing the Israelites. The word for "great wrath" is typically used for the wrath of a god, but notice that the verse doesn't mention who the source of the wrath was. We know that God had directed the three kings to destroy Moab, so it would not have been from God unless the armies had violated His laws, which is not stated. It could not actually be from Chemosh because idols have no power -- they aren't real. However, it makes sense that the superstitious Israelites might assume Chemosh did have power, so they gave up and went home. This was Israel's battle, and with them leaving, the other two kings had no reason to stay.

Thus, the great victory given to the three kings because God respected Jehoshaphat ended abruptly. There was no profit from this battle, no celebration. Israel's army did not trust God. They had no steadfast loyalty to Him. This confirms the point made in II Kings 3:10 that Jehoram did not trust God. He started the battle assuming he would lose and left just before the end, thinking he was defeated. However, the only thing that defeated him was his imagination.