Then Jonathan said to David, "Tomorrow is the New Moon; and you will be missed, because your seat will be empty.
1 Samuel 20:18
Surrounding context
20:17 Now Jonathan again caused David to vow, because he loved him; for he loved him as he loved his own soul.
20:18 Then Jonathan said to David, "Tomorrow is the New Moon; and you will be missed, because your seat will be empty.
20:19 And when you have stayed three days, go down quickly and come to the place where you hid on the day of the deed; and remain by the stone Ezel.