During the first two centuries the gospel was taken from place to place by travelling evangelists and teachers. Believers customarily took these missionaries into their homes and gave them provisions for their journey when they left. Since Gnostic teachers also relied on this practice, 2 John was written to urge discernment in supporting travelling teachers.
This epistle is like an abridgement of the first; it touches, in few words, on the same points. The Elect Lady is commended for her virtuous and religious education of her children; is exhorted to abide in the doctrine of Christ, to persevere in the truth, and carefully to avoid the delusions of false teachers. But chiefly the apostle beseeches her to practice the great commandment of Christian love and charity.Matthew Henry