31 These are the nations that the Lord left in the land to test those Israelites who had not experienced the wars of Canaan. 2 He did this to teach warfare to generations of Israelites who had no experience in battle. 3 These are the nations: the Philistines (those living under the five Philistine rulers), all the Canaanites, the Sidonians, and the Hivites living in the mountains of Lebanon from Mount Baal-hermon to Lebo-hamath. 4 These people were left to test the Israelites-to see whether they would obey the commands the Lord had given to their ancestors through Moses.
Matthew Henry's Commentary on Judges 3:1-4
Commentary on Judges 3:1-7
(Read Judges 3:1-7)
As the Israelites were a type of the church on earth, they were not to be idle and slothful. The Lord was pleased to try them by the remains of the devoted nations they spared. Temptations and trials detect the wickedness of the hearts of sinners; and strengthen he graces of believers in their daily conflict with Satan, sin, and this evil world. They must live in this world, but they are not of it, and are forbidden to conform to it. This marks the difference between the followers of Christ and mere professors. The friendship of the world is more fatal than its enmity; the latter can only kill the body, but the former murders many precious souls.