1 Samuel 18:17-21

17Saul said to David, “Here is my older daughter Merab. I will give her to you in marriage; only serve me bravely and fight the battles of the Lord.” For Saul said to himself, “I will not raise a hand against him. Let the Philistines do that!”

18But David said to Saul, “Who am I, and what is my family or my clan in Israel, that I should become the king’s son-in-law?”

19So when the time came for Merab, Saul’s daughter, to be given to David, she was given in marriage to Adriel of Meholah.

20Now Saul’s daughter Michal was in love with David, and when they told Saul about it, he was pleased.

21“I will give her to him,” he thought, “so that she may be a snare to him and so that the hand of the Philistines may be against him.” So Saul said to David, “Now you have a second opportunity to become my son-in-law.”