1 Samuel 18:14-18

And David behaved himself wisely in all his ways; and the LORD was with him.

Wherefore when Saul saw that he behaved himself very wisely, he was afraid of him.

But all Israel and Judah loved David, because he went out and came in before them.

And Saul said to David, Behold my elder daughter Merab, her will I give thee to wife: only be thou valiant for me, and fight the LORD’s battles. For Saul said, Let not mine hand be upon him, but let the hand of the Philistines be upon him.

And David said unto 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?