Charles Ellicott Commentary 1 Chronicles 18:12

"Moreover Abishai the son of Zeruiah smote of the Edomites in the Valley of Salt eighteen thousand." — 1 Chronicles 18:12 (ASV)

Moreover Abishai ... —Hebrew, And Abishai son of Zeruiah had smitten Edom in the Valley of Salt, eighteen thousand.

In Samuel we read something quite different: And David made a name, when he returned from his smiting Aram. “Aram” should be read Edom, as the Septuagint, Syriac, and Arabic have it. Perhaps, also, the text of Samuel is further corrupted. (Compare to 1 Kings 11:15 and Psalm 60 (title).) From a comparison of the three passages it appears that Edom took advantage of David’s absence to invade Judah, after which the king detached a column of his forces, and sent them south under Joab and Abishai to repulse the new enemy.

Valley of salt. — 2 Kings 14:7