1 Samuel 18:17-21

17Then Saul said to David, “Behold I will give you my older daughter Merab as a wife; only be brave for me and fight the Lord’s battles.” For Saul thought, “My hand shall not be against him, but let the hand of the Philistines be against him.”

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

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

20Now Michal, Saul’s daughter, loved David; and when they told Saul, it pleased him.

21Saul said, “I will give her to him so that she may become a snare (bad influence, source of trouble) to him, and that the hand of the Philistines may be against him.” So Saul said to David for a second time, “You shall be my son-in-law today.”