NET
15 “This is what the Sovereign Lord says: ‘The Philistines have exacted merciless revenge, showing intense scorn in their effort to destroy Judah with unrelenting hostility.
Darby
15 Thus saith the Lord Jehovah: Because the Philistines have dealt by revenge, and have taken vengeance with despite of soul, to destroy, from old hatred;
KJV
15 Thus saith the Lord GOD; Because the Philistines have dealt by revenge, and have taken vengeance with a despiteful heart, to destroy [it] for the old hatred;