David said to Jonathan, Behold, tomorrow is the new moon, and I should not fail to sit with the king at meat: but let me go, that I may hide myself in the field to the third day at evening.
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).