Then Jonathan and David made a covenant, because he loved him as his own soul. (18:3)

And Jonathan stripped himself of the robe that [was] upon him, and gave it to David, and his garments, even to his sword, and to his bow, and to his girdle. (18:4)

So Jonathan made [a covenant] with the house of David, [saying], Let the Lord even require [it] at the hand of David's enemies. (20:16)

And Jonathan said to David, Go in peace, forasmuch as we have sworn both of us in the name of the Lord, saying, The Lord be between me and thee, and between my seed and thy seed for ever. And he arose and departed: and Jonathan went into the city. (20:42)

--2 Samuel--

But the king spared Mephibosheth, the son of Jonathan the son of Saul, because of the LORD'S oath that [was] between them, between David and Jonathan the son of Saul. (21:7)