Judges 3:1-4

Now these are the nations which Yahweh left, to prove Israel by them, even as many [of Israel] as had not known all the wars of Canaan;

only that the generations of the children of Israel might know, to teach them war, at the least such as before knew nothing of it:

[namely], the five lords of the Philistines, and all the Canaanites, and the Sidonians, and the Hivites who lived on Mount Lebanon, from Mount Baal-hermon to the entrance of Hamath.

They were [left], to prove Israel by them, to know whether they would listen to the commandments of Yahweh, which he commanded their fathers by Moses.