Jonathan said, Far be it from you; for if I should at all know that evil were determined by my father to come on you, then wouldn't I tell you that?
There are several oaths and strong affirmations in this chapter (1 Samuel 20:3; 1 Samuel 20:12-13; 1 Samuel 20:16-17; 1 Samuel 20:23; 1 Samuel 20:42). The one that David made in 1 Samuel 20:3 is very strong. He believed correctly that he was in mortal danger, and he tried to make Jonathan see this. Jonathan was open to anything David wanted to suggest to prove his point (1 Samuel 20:4).