1 Samuel 20:15

Then Jonathan cut a covenant with David because he loved him as his own soul.

“As for the agreement of which you and I have spoken, behold, Yahweh is between you and me forever.”

And Jonathan said to David, “Go in peace, inasmuch as we have sworn to each other in the name of Yahweh, saying, ‘Yahweh will be between me and you, and between my seed and your seed forever.’” Then he rose and departed, while Jonathan went into the city.

So the two of them cut a covenant before Yahweh; and David stayed at Horesh while Jonathan went to his house.

“So now swear to me by Yahweh that you will not cut off my seed after me and that you will not destroy my name from my father’s household.”

Then David said, “Is there yet anyone left of the house of Saul, that I may show him lovingkindness for Jonathan’s sake?”

But the king spared Mephibosheth, the son of Jonathan the son of Saul, because of the oath of Yahweh which was between them, between David and Saul’s son Jonathan.