“I know that after my departing grievous wolves will enter in among you, not sparing the flock, and from among your own selves will men arise, speaking perverse things, to draw away the disciples after them.”
He warns that the attacks will come from without and within. Wolves will find their way in from outside, deceitful, lying, thieving shepherds will be found inside. Neither will spare the flock. Men, themselves being deceived, will deceive others. He had already witnessed this himself in the troubles brought on the churches by the Judaisers.
For false prophets as wolves see Matthew 7:15. For the opponents and antagonistic authorities as wolves see Matthew 10:16; Luke 10:3. The consequences of men who have offered themselves as teachers of truth but have in fact simply led men astray are so obvious today that little needs to be said. And the sad thing is that they are often the nicest of men, for it is the art of the con man, even the unconscious con man, to be nice.
That this began at some stage to happen in the Ephesian church comes out in that later Paul left Timothy with them, and one of the reasons for his doing so was in order to deal with some who were seeking to lead others astray (1 Timothy 1:3-8; 1 Timothy 1:20; 1Ti 4:1-7; 1 Timothy 6:3-6; 1 Timothy 6:20-21). There would of course have been a number of different assemblies in the large Ephesian church. We must not necessarily see the whole church as affected. But it was clearly an important issue.