Acts 20:29-30 29I know that after my departure, fierce wolves will come in among you, not sparing the flock; 30and from among your own selves will arise men speaking perverted things in order to draw away the disciples after them.
Paul next gave the reason why the leaders needed to be diligent and careful about caring for the church. Speaking from his own ministry experience and insight provided by the Holy Spirit, Paul warned of a problem that would arise in Ephesus and other cities. One of the many challenges he faced in his ministry was those who tried to distort and twist his words. Continuing his use of the shepherding metaphor, he warned about fierce wolves who would try to steal the sheep by false teaching. They would twist the truth of the gospel out of selfish motives, making followers of themselves.
These false teachers would come from within the church and from outside. Those from outside the church would be like ravenous wolves, hungry to eat the sheep. The image is strong and expresses the danger of accepting outside teachers or leaders without careful vetting and character testing. The Ephesians should not listen to any person who claimed to be a knowledgeable teacher. Wandering sophists were common in many of ancient cities. People found entertainment by going down to the market or forum to listen to such teachers. In many places in his travels, Paul appeared to be such a person. The problem was that such persons could sound convincing, and they could even have a bit of the truth, but they could easily deceive people who were not firmly grounded in truth. Other New Testament writings indicate that such false teachers did come to Ephesus and other cities (Ephesians 5:6–14; Colossians 2:8; Revelation 2:2).
The other type of false teachers would arise from within the church. These people would also be deceptive, but some of this would come from their own ignorance or ungodly character. Their biggest and perhaps most subtle danger would be that they would focus on themselves. In ministry leadership, one of the most dangerous temptations is to begin to think of oneself more highly than one should. We can become the focus with our good rhetoric (preaching ability) or people gifts (great personality). Paul later wrote to Timothy about this very problem arising in Ephesus (1 Timothy 1:19-20.; 4:1–3; 2 Timothy 1:15; 2:17-18; 3:1–9). Heresy can come from outside and inside the church.
The answer is to have godly and sanctified leaders who can then train the church to adhere to the truth of the gospel. Paul’s personal ministry and letters had a powerful influence in keeping the church united in orthodoxy, which is one of the reasons his letters were recognized as inspired and later canonized by the church. He knew that when he was gone and his influence not as powerful, the churches he planted would be tempted to compromise their teaching and ethics. God did not let that happen by continuing Paul’s influence through his writings.