1 Samuel 20:12-17

And Jonathan said unto David, O LORD God of Israel, when I have sounded my father about to morrow any time, or the third day, and, behold, if there be good toward David, and I then send not unto thee, and shew it thee; the LORD do so and much more to Jonathan: but if it please my father to do thee evil, then I will shew it thee, and send thee away, that thou mayest go in peace: and the LORD be with thee, as he hath been with my father. And thou shalt not only while yet I live shew me the kindness of the LORD, that I die not: but also thou shalt not cut off thy kindness from my house for ever: no, not when the LORD hath cut off the enemies of David every one from the face of the earth. So Jonathan made a covenant with the house of David, saying, Let the LORD even require it at the hand of David's enemies. And Jonathan caused David to swear again, because he loved him: for he loved him as he loved his own soul.