Saul replied, “Say to David, ‘The king wants no other price for the bride than a hundred Philistine foreskins, to take revenge on his enemies.’” Saul’s plan was to have David fall by the hands of the Philistines.
When the attendants told David these things, he was pleased to become the king’s son-in-law. So before the allotted time elapsed, David took his men with him and went out and killed two hundred Philistines and brought back their foreskins. They counted out the full number to the king so that David might become the king’s son-in-law. Then Saul gave him his daughter Michal in marriage.
(1 Samuel 18:25-27)