I Samuel 20:12-17

Then Jonathan said to David: “The LORD God of Israel is witness! When I have sounded out my father sometime tomorrow, or the third day, and indeed there is good toward David, and I do not send to you and tell you, may the LORD do so and much more to Jonathan. But if it pleases my father to do you evil, then I will report it to you and send you away, that you may go in safety. And the LORD be with you as He has been with my father. And you shall not only show me the kindness of the LORD while I still live, that I may not die; but you shall not cut off your kindness from my house forever, no, not when the LORD has cut off every one of the enemies of David from the face of the earth.” So Jonathan made a covenant with the house of David, saying, “Let the LORD require it at the hand of David’s enemies.” Now Jonathan again caused David to vow, because he loved him; for he loved him as he loved his own soul.