1 Samuel 18:17

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.

My elder daughter Merab, her will I give thee to wife. Though bound to this already, he had found it convenient to forget his former promise, and now holds it out as a new offer, which would tempt David to give additional proofs of his valour.

Only be thou valiant for me. But the fickle and perfidious monarch broke his pledge at the time when the marriage was on the eve of being celebrated, and bestowed Merab on another man (see the note at 2 Samuel 21:8) - an indignity as well as a wrong, which was calculated deeply to wound the feelings and provoke the resentment of David. Perhaps it was intended to do so, that advantage might be taken of his indiscretion. But David was preserved from this snare.