1 Samuel 18:17-21

17Finally, Saul said to David, “Here is my oldest daughter Merab. I will give her to you as your wife if you prove yourself to be a warrior for me and fight the Lord’s battles.” (Saul thought, “I must not lay a hand on him. Let the Philistines do that.”)

18“Who am I?” David asked Saul. “And how important are my relatives or my father’s family in Israel that I should be the king’s son-in-law?”

19But when the time came to give Saul’s daughter Merab to David, she was married to Adriel from Meholah.

20However, Saul’s daughter Michal fell in love with David. When Saul was told about it, the news pleased him.

21Saul thought, “I’ll give her to David. She will trap him, and the Philistines will get him.” So he said to David a second time, “You will now be my son-in-law.”