1 Samuel 20:9
And Jonathan said, Far be it from thee: for if I knew certainly that evil were determined by my father to come upon thee, then would not I tell it thee? And Jonathan said, Far be it from thee: for if I knew certainly that evil were determined by my father to come upon thee, then would not I tell it thee?
David came to Jonathan conscious of his innocence, asking what he had done to make Saul seek his life. Jonathan at first refused to believe that Saul still intended to kill David. He assured David that Saul had changed his purpose and would do nothing great or small without telling him, and would not hide such a plan from him.
He reasoned this way because of the remarkable display of God's power in restraining Saul at Ramah. He felt his father could not still harm David, since that would be open rebellion against God. David was not convinced by Jonathan's assurance and remained certain that his life was still in danger.
The verse expresses Jonathan's love for David as for his own soul, with his soul knit to David's soul in a covenant to be united as brothers. In the verse Jonathan pledges to tell David if he knows certainly that evil has been determined by Saul to come upon him. God brought about that sacred bond and in his providence used Jonathan to preserve David's life when Saul tried to kill him as Israel's future ruler.