John Gill Commentary 2 Chronicles 25:11

"And Amaziah took courage, and led forth his people, and went to the Valley of Salt, and smote of the children of Seir ten thousand." — 2 Chronicles 25:11 (ASV)

And Amaziah strengthened himself, and led forth his people ,
&c.] To go to war with the Edomites; not discouraged by the dismission of the hired troops, but trusting in the promise and power of God, he went forth with boldness and intrepidity:

and went to the valley of salt, and smote of the children of Seir,
ten thousand ;
the Edomites; so called, not because they were the posterity of Seir, but because they dwelt in Seir, from whence they drove the descendants of Seir, and dwelt in their stead; see (2 Kings 14:7) .