Acts 20:28-31

Be on guard for yourselves and for all the flock among which the Holy Spirit has appointed you as overseers, to shepherd the church of God which he obtained through the blood of his own Son. I know that after my departure fierce wolves will come in among you, not sparing the flock. And from among you yourselves men will arise, speaking perversions of the truth in order to draw away the disciples after them. Therefore be on the alert, remembering that night and day for three years I did not stop warning each one of you with tears.