The Acts 20:28-31

Take heed unto yourselves, and to all the flock, in the which the Holy Ghost hath made you bishops, to feed the church of God, which he purchased with his own blood. I know that after my departing grievous wolves shall enter in among you, not sparing the flock; and from among your own selves shall men arise, speaking perverse things, to draw away the disciples after them. Wherefore watch ye, remembering that by the space of three years I ceased not to admonish every one night and day with tears.