Acts 20:28-31

So keep watch over yourselves and over all the flock which the Holy Spirit has placed in your care. Be shepherds of the church of God, which he made his own through the blood of his Son. I know that after I leave, fierce wolves will come among you, and they will not spare the flock. The time will come when some men from your own group will tell lies to lead the believers away after them. Watch, then, and remember that with many tears, day and night, I taught every one of you for three years.