To prove Israel That their piety and faithfulness to the one living and true God might appear, if they did not imitate these nations, and relapse into idolatry, and their baseness and degeneracy if they did. To know whether they would hearken That is, that they themselves and others might know by experience.
Related Commentaries of Judges 3:4
Judges 3:4
4 And they were to prove Israel by them, to know whether they would hearken unto the commandments of the LORD, which he commanded their fathers by the hand of Moses.