Acts 20:28-31

Be on guard for yourselves and for all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood. I know that after my departure savage wolves will come in among you, not sparing the flock; and from among your own selves men will arise, speaking perverse things, to draw away the disciples after them. Therefore be on the alert, remembering that night and day for a period of three years I did not cease to admonish each one with tears.