1 Samuel 20:17

Now it happened when he had finished speaking to Saul, that the soul of Jonathan was knit to the soul of David, and Jonathan loved him as his own soul.

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

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.

Then Gedaliah the son of Ahikam, the son of Shaphan, swore to them and to their men, saying, “Do not be afraid of serving the Chaldeans; stay in the land and serve the king of Babylon, that it may go well with you.