'Foreskins' in the Bible

Then Saul said, “This is what you shall say to David: ‘The king wants no dowry except a hundred foreskins of the Philistines, to take vengeance on the king’s enemies.’” Now Saul’s intention was to cause David’s death at the hand of the Philistines.

David arose and went, he and his men, and killed two hundred Philistine men, and David brought their foreskins [as proof of death] and presented every one of them to the king, so that he might become the king’s son-in-law. So Saul gave him Michal, his [younger] daughter, as a wife.