These are the nations the LORD left to test1 all those Israelites who had not experienced any of the wars in Canaan
References for Judges 3:1
(he did this only to teach warfare to the descendants of the Israelites who had not had previous battle experience):
the five2 rulers of the Philistines,3 all the Canaanites, the Sidonians, and the Hivites4 living in the Lebanon mountains from Mount Baal Hermon5 to Lebo Hamath.6
References for Judges 3:3
They were left to test7 the Israelites to see whether they would obey the LORD's commands, which he had given their forefathers through Moses.
References for Judges 3:4