Only problem is, that's not what it says. Here's the real verse (with the two prior leading up to it to give context):
15 "This is what the Sovereign LORD says: 'Because the Philistines acted in vengeance and took revenge with malice in their hearts, and with ancient hostility sought to destroy Judah, 16 therefore this is what the Sovereign LORD says: I am about to stretch out my hand against the Philistines, and I will cut off the Kerethites and destroy those remaining along the coast. 17 I will carry out great vengeance on them and punish them in my wrath. Then they will know that I am the LORD, when I take vengeance on them.' "