1 Samuel 24:20-24

Now, behold, I know that you will certainly be king, and that the kingdom of Israel will be established in your hand.

So now swear to me by the Lord that you will not cut off my descendants after me, and that you will not eliminate my name from my father’s household.”

And David swore an oath to Saul. Then Saul went to his home, but David and his men went up to the stronghold.