Amos 2:1

For he burnt the bones etc.—Once the king of Edom fell into the hands of the king of Moab, and they burned his bones and plastered them on the walls of the house, and the Holy One, blessed be He, requited the injustice inflicted upon the king, for they treated him with disgrace.

"Thus said the LORD... because he burned the bones of the king of Edom into lime." This is what is said in the book of Kings: "He took his firstborn son who was to reign after him and offered him up as a burnt offering on the wall. And there was a great wrath against Israel..." The wrath was from the king of Edom against Israel, from that day forward, since the king of Moab burned the son of the king of Edom...

And the decree regarding Moab is mentioned here when the prophet says "for three trangressions of Moab I will overlook and for the fourth I will not overlook. Because they burned the bones of the Edomite king to lime" And with the other nations mentioned above, Damascus, Aza, Tzur, Edom and Amon their fourth sin was regarding Israel, but Moab's sin we don't understand why it was listed here when he acted against Edom who is the enemy of Gd. And Rashi write about a time when the king of Edom fell and they burnt his bones and ground them into the walls of the house. And Gd decreed regarding the humiliation and afflictation of this king. And anothe commentary says that burning the bones of the king of Edom was a humiliation and Edom is still the child of Yitzchak. But these are not the true answers. In my opinion the prophecies are in a specific order beginning with Damascus who fought in Gilead in a humiliating way. Then it discusses Aza and Tzur who both were punished for rebellion and breaking the peace treaty between them and Israel to send them to Edom. And afterwards the prophet discusses Edom to tell us about the war between Edom and Israel during which the Philistines, Tzur and Aza gave over the refugees. And it discusses the wickedness of Edom who curbed their compassion.

And after discussing the wars in Damascus and Edom the prophet returns to the rebellion of Aza and Tzur and says what their reason was in these two wars. The Damascus used the iron furrows on the residents of Gilead in order to do the same thing that Amon tried to do and to increase their borders. The men of Damascus learned from Amon. Then the prophet discusses the factors behind the hatred and war between Edom and Israel. They were allies with Israel and Judah and went to fight Moab. The king of Moab during that fight took the King Adom and brought him up on the wall and burned him as an offering to his god. And the "offering" was completely burned up to "lime" meaning until the bones were soft as dust. And this created animosity between the Edomites and the Israelites because Israel brought them into a war that ended up with the crown prince getting burned. And from them on the animosity between Israle and Edom increased and they were in a constant state of war between them until the point when the Philistines gave the Israelite refugees to Edom. So Moab was the cuase of the animosity between Israel and Edom and the cause of the war