1 Samuel 18:17-21

17Then Saul said to David, “Here is my older daughter Merab; I will give her to you as a wife. Only be valiant for me, and fight the Lord’s battles.” For Saul thought, “Let my hand not be against him, but let the hand of the Philistines be against him.”

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

19But it happened at the time when Merab, Saul’s daughter, should have been given to David, that she was given to Adriel the Meholathite as a wife.

20Now Michal, Saul’s daughter, loved David. And they told Saul, and the thing pleased him.

21So Saul said, “I will give her to him, that she may be a snare to him, and that the hand of the Philistines may be against him.” Therefore Saul said to David a second time, “You shall be my son-in-law today.”