1 Samuel 18:23-25

23Saul's servants said this to David. But David replied, ‘It is a great honour for someone to marry the king's daughter. But I am poor. I am not important enough.’

24Saul's servants told him what David had said.

25Saul said, ‘Tell David this: The king does not want David to pay money to marry the king's daughter. He can pay for her with the foreskins of 100 dead Philistines. Saul wants David to punish his enemies.’ In this way, Saul thought that he would use the Philistines to kill David.