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From the very beginning (Deuteronomy 2:16-20) of their history till we lose sight of them (Judges 5:2), this tribe is closely associated with the Moabites (Judges 10:11; 2 Chronicles 20:1; Zeph. 2:8).
Both of these tribes hired Balaam to curse Israel (Deuteronomy 23:4). The Ammonites were probably more of a predatory tribe, moving from place to place, while the Moabites were more settled. They inhabited the country east of the Jordan and north of Moab and the Dead Sea, from which they had expelled the Zamzummims or Zuzims (Deuteronomy 2:20; Genesis 14:5). They are known as the Beni-ammi (Genesis 19:38), Ammi or Ammon being worshipped as their chief god.
They showed no kindness to the Israelites when passing through their territory, and therefore they were prohibited from “entering the congregation of the Lord to the tenth generation” (Deuteronomy 23:3).
Afterwards, they became hostile to Israel (Judges 3:13). Jephthah waged war against them, and took “twenty cities… with a very great slaughter” (Judges 11:33). They were again defeated by Saul (1 Samuel 11:11). David also defeated them and their allies the Syrians (2 Samuel 10:6-14), and took their chief city, Rabbah, with much spoil (2 Samuel 10:14; 12:26-31). The subsequent events of their history are noted in 2 Chronicles 20:25; 26:8; Jeremiah 49:1; Ezek. 25:3, 6.
The national idol worshipped by this people was Molech or Milcom, at whose altar they offered human sacrifices (1 Kings 11:5, 7). The high places built for this idol by Solomon, at the instigation of his Ammonite wives, were not destroyed till the time of Josiah (2 Kings 23:13).