1 Samuel 18:21-22, 29

He thought, “I will let her marry David. Then she will be a trap for him, and the Philistines will defeat him.” So Saul said to David a second time, “You may become my son-in-law.” And Saul ordered his servants to talk with David in private and say, “Look, the king likes you. His servants love you. You should be his son-in-law.”

So he grew even more afraid of David, and he was David’s enemy all his life.