He goes on to warn against those who deny the truth of Christ and to stand guard against letting these naysayers turn those who have believed against their beliefs. Once you identify such a person keep them out of your meetings for if you allow them to speak their lies, you are basically as guilty as them.
So be alert and don't be shy about protecting the work that has been done. I think it is reminiscent of a shepherd protecting his flock.
In third John the Apostle John is writing a personal letter to his friend Gaius. In this letter he commends him for caring so well for the teachers that pass through his areas and tell him of how these travelers have told of the goodness they share with them. He kind of lets him know how much the teachers rely on him as they don't take any assistance from unbelievers.
John also alerts Gaius of the dissension caused by Diotrephes, to the point that those he has targeted, he puts out of the church. He encourages Gaius to follow the good and true teaching and not to be swayed by those who are causing issues. He ends with a conclusion typical for such letters.
I apologize for this being late and brief. I have been blessed to preach the last two weeks at a wonderful church in the area. I have not preached for many years and it has taken much of my time. Blessings to all.