Albert Barnes Commentary 1 Samuel 15:4

"And Saul summoned the people, and numbered them in Telaim, two hundred thousand footmen, and ten thousand men of Judah." — 1 Samuel 15:4 (ASV)

Telaim - Probably the same as “Telem” (Joshua 15:24), one of the most remote cities of Judah, toward the coast of Edom. The name means “lambs” and was likely so called because of the numerous flocks.

Two hundred thousand ... - A striking contrast with the six hundred men who composed his whole army before (1 Samuel 13:15), and a proof of how completely the Philistines had been driven back for a time. The separate mention of the men of Judah shows how little union there was between Judah and Ephraim even at this time, a circumstance that sheds light on the entire subsequent history.