Adam Clarke on Judges 13:1

Delivered them into the hand of the Philistines - It does not appear that after Shamgar, to the present time, the Philistines were in a condition to oppress Israel, or God had not permitted them to do it; but now they have a commission, the Israelites having departed from the Lord. Nor is it evident that the Philistines had entirely subjected the Israelites, as there still appears to have been a sort of commerce between the two people. They had often vexed and made inroads upon them, but they had them not in entire subjection; see Jdg 15:11.