These are so simple in their object and structure, however important for the truth and those that love it, as to need but few words. The sister, an unnamed lady, is solemnly warned not to receive one untrue to the doctrine of Christ, i.e. of His person, the foundation and the substance of all truth. The brother, who of course is named, is exhorted in the face of personal or party opposition to persevere in the love which had characterized him, to receive faithful souls, though strangers, who went forth for the Name. The wisdom as well as the value of these letters is great. Women in particular might feel no small difficulty in refusing plausible men who seemed zealous in the Lord's work. It might be an evangelist once blessed in winning souls; or an elder like some in Ephesus of whom Paul spoke as getting astray. But when the spirit of error is abroad, truth decides and not office merely can avail. On the other hand the good brother is not to be alarmed by the anger of a Diotrephes but is to welcome such as go forth truly for the Lord's name, and thus encourage a Demetrius who might otherwise be frowned down. How admirably the Holy Spirit led to counsels for-guiding us in the evil day!
The First Epistle of John