1 Samuel 18:20-22, 28-29

Meanwhile, Saul’s daughter Michal was in love with David. When Saul was told of this, he rubbed his hands in anticipation. “Ah, a second chance. I’ll use Michal as bait to get David out where the Philistines will make short work of him.” So again he said to David, “You’re going to be my son-in-law.” Saul ordered his servants, “Get David off by himself and tell him, ‘The king is very taken with you, and everyone at court loves you. Go ahead, become the king’s son-in-law!’”

As Saul more and more realized that GOD was with David, and how much his own daughter, Michal, loved him, his fear of David increased and settled into hate. Saul hated David.