You’re missing a key part to the story, Saul (no, not that Saul/Paul) was buying selling a human woman with those foreskins.
And who was the person who wanted traded these foreskins in exchange for the human woman? David, as in, David and Goliath.
Edit: swapped the vendor/purchaser. I left the religion about 20 years ago, so I should probably fact-check myself before posting.