1 Samuel 20:7, 9, 33

If he says, ‘All right,’ your servant will be safe; but if he is very angry, then be certain that he has decided on evil.

Jonathan said, “Far be it from [happening to] you! In fact, if I indeed learn that my father has decided to harm you, would I not tell you about it?”

Then Saul hurled his spear at him to strike him down, so Jonathan knew [without any doubt] that his father had decided to put David to death.