1 Samuel 20:30-33

30Saul became angry with Jonathan and said to him, “You stupid traitor! Don’t I realize that to your own disgrace and to the disgrace of your mother’s nakedness you have chosen this son of Jesse?

31For as long as this son of Jesse is alive on the earth, you and your kingdom will not be established. Now, send some men and bring him to me. For he is as good as dead!”

32Jonathan responded to his father Saul, “Why should he be put to death? What has he done?”

33Then Saul threw his spear at Jonathan in order to strike him down. So Jonathan was convinced that his father had decided to kill David.