1 Samuel 20:11-17

Jonathan said to David, “Come on. Let’s go out to the field.” When the two of them had gone out into the field, Jonathan said to David, “The LORD God of Israel is my witness. I will feel out my father about this time the day after tomorrow. If he is favorably inclined toward David, will I not then send word to you and let you know? But if my father intends to do you harm, may the LORD do all this and more to Jonathan, if I don’t let you know and send word to you so you can go safely on your way. May the LORD be with you, as he was with my father. While I am still alive, extend to me the loyalty of the LORD, or else I will die! Don’t ever cut off your loyalty to my family, not even when the LORD has cut off every one of David’s enemies from the face of the earth and called David’s enemies to account.” So Jonathan made a covenant with the house of David. Jonathan once again took an oath with David, because he loved him. In fact Jonathan loved him as much as he did his own life.