Charles Spurgeon Commentary 1 Samuel 20:2-3

"And he said unto him, Far from it; thou shalt not die: behold, my father doeth nothing either great or small, but that he discloseth it unto me; and why should my father hide this thing from me? it is not so. And David sware moreover, and said, Thy father knoweth well that I have found favor in thine eyes; and he saith, Let not Jonathan know this, lest he be grieved: but truly as Jehovah liveth, and as thy soul liveth, there is but a step between me and death." — 1 Samuel 20:2-3 (ASV)

Behold, my father will do nothing either great or small, but that he will shew it me; and why should my father hide this thing from me? It is not so. And David sware moreover, and said, Thy father certainly knoweth that I have found grace in thine eyes; and he saith, Let not Jonathan know this, lest he be grieved: but truly as the LORD liveth, and as thy soul liveth, there is but a step between me and death.

He had so often escaped, as it were by the skin of his teeth, from his cruel persecutor, that he knew himself to be in a position of extreme peril.