1 Samuel 18:16-20

But all Israel and Judah loved David, for he would go out to battle and return before them.

Then Saul said to David, “Here is my older daughter Merab; I will give her to you as a wife, only be a valiant man 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.”

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

So it came about at the time that Merab, Saul’s daughter, was to be given to David, that she was given instead to Adriel the Meholathite as a wife. David Marries Saul’s Daughter

Now Michal, Saul’s daughter, loved David. When they informed Saul, the thing was pleasing to him.