1 Samuel 20:11 (KJV)

If thy father at all miss me, then say, David earnestly asked leave of me that he might run to Bethlehem his city: for there is a yearly sacrifice there for all the family.

If he say thus, It is well; thy servant shall have peace: but if he be very wroth, then be sure that evil is determined by him.

Therefore thou shalt deal kindly with thy servant; for thou hast brought thy servant into a covenant of the LORD with thee: notwithstanding, if there be in me iniquity, slay me thyself; for why shouldest thou bring me to thy father?

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?

Then said David to Jonathan, Who shall tell me? or what if thy father answer thee roughly?

And Jonathan said unto David, O LORD God of Israel, when I have sounded my father about to morrow any time, or the third day, and, behold, if there be good toward David, and I then send not unto thee, and shew it thee;

The LORD do so and much more to Jonathan: but if it please my father to do thee evil, then I will shew it thee, and send thee away, that thou mayest go in peace: and the LORD be with thee, as he hath been with my father.

And thou shalt not only while yet I live shew me the kindness of the LORD, that I die not:

But also thou shalt not cut off thy kindness from my house for ever: no, not when the LORD hath cut off the enemies of David every one from the face of the earth.

So Jonathan made a covenant with the house of David, saying, Let the LORD even require it at the hand of David's enemies.