1 Samuel 20:21 (KJV)

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

And Jonathan caused David to swear again, because he loved him: for he loved him as he loved his own soul.

Then Jonathan said to David, To morrow is the new moon: and thou shalt be missed, because thy seat will be empty.

And when thou hast stayed three days, then thou shalt go down quickly, and come to the place where thou didst hide thyself when the business was in hand, and shalt remain by the stone Ezel.

And I will shoot three arrows on the side thereof, as though I shot at a mark.

But if I say thus unto the young man, Behold, the arrows are beyond thee; go thy way: for the LORD hath sent thee away.

And as touching the matter which thou and I have spoken of, behold, the LORD be between thee and me for ever.

So David hid himself in the field: and when the new moon was come, the king sat him down to eat meat.

And the king sat upon his seat, as at other times, even upon a seat by the wall: and Jonathan arose, and Abner sat by Saul's side, and David's place was empty.

Nevertheless Saul spake not any thing that day: for he thought, Something hath befallen him, he is not clean; surely he is not clean.