Charles Ellicott Commentary 2 Chronicles 20:1

"And it came to pass after this, that the children of Moab, and the children of Ammon, and with them some of the Ammonites, came against Jehoshaphat to battle." — 2 Chronicles 20:1 (ASV)

It came to pass after this also. — Rather, And it came to pass afterwards, that is, after the battle of Ramoth-Gilead, and Jehoshaphat’s reformation of law and religion.

And the children of Ammon, and with them other beside the Ammonites. — This is an attempt to get a reasonable sense out of a corrupted text. What the Hebrew says is: And the sons of Ammon, and with them some of the Ammonites.

So the Vulgate, “et filii Ammon et cum eis de Ammonitis.” Transpose a single Hebrew letter, and there results the intelligible reading: And the sons of Ammon, and with them the Maonites (Hebrew, Me’ûnîm. See on 1 Chronicles 4:41–42). The Maonites are mentioned again (2 Chronicles 26:7) in company with Arabs. They appear to have been a tribe, whose chief seat was Maon, on the eastern slopes of the chain of Mount Seir, after which they are called “sons,” or “inhabitants of Mount Seir” in 2 Chronicles 20:10; 2 Chronicles 20:22–23.

Accordingly Josephus (Antiquities ix. 1, § 2) calls them a multitude of Arabs.

The Septuagint reads: “And with them some of the Minaioi,” a name which possibly represents the me’înîm of the Hebrew text of 1 Chronicles 4:41. The Syriac version says, “and with them men of war;” and the Arabic, “brave men.”

Perhaps the expression rendered and with them—we’immahèm—is a relic of an original reading, and the Maonites; and the phrase some of the Ammonites (mçhâ’ammônîm), which follows, is merely a gloss on an obscure name by some transcriber.