Acts 20:28-31

Take care and be on guard for yourselves and the whole flock over which the Holy Spirit has appointed you bishops and guardians, to shepherd (tend and feed and guide) the church of the Lord or of God which He obtained for Himself [buying it and saving it for Himself] with His own blood. I know that after I am gone, ferocious wolves will get in among you, not sparing the flock; Even from among your own selves men will come to the front who, by saying perverse (distorted and corrupt) things, will endeavor to draw away the disciples after them [to their own party]. Therefore be always alert and on your guard, being mindful that for three years I never stopped night or day seriously to admonish and advise and exhort you one by one with tears.