By this shall all men know,.... Not only by this you yourselves will know that ye have passed from death to life, that the true work of grace is begun upon your hearts; nor only by this will you know one another to be Christians; but by this all men, even the men of the world will know,that ye are my disciples, if ye have love one to another: and own and acknowledge it, as Tertullian says the very Heathens did in his time; who would say, when they saw the Christians pass along the streets, and meet and express their affection to each other, "see how they love one another": would to God the same was as observable now.
The distinguishing badge and character of a disciple of Christ, is not any outward garb, or any austerities of life, by which the disciples of John and of the Pharisees were known; nor were the ordinary nor extraordinary gifts of the Spirit, bestowed upon the disciples of Christ, what distinguished them as such; since those who were not truly his disciples, had these bestowed on them; but love to one another, brotherly love was the distinguishing character, and this is another reason or argument enforcing a regard unto it.
Apolog. c.