Albert Barnes Commentary 1 Samuel 17:2

"And Saul and the men of Israel were gathered together, and encamped in the vale of Elah, and set the battle in array against the Philistines." — 1 Samuel 17:2 (ASV)

The valley of Elah - that is, of the terebinth, now called Wady es-Sunt, from the acacias which are scattered in it.