1:4-6 It is good to be trained to early religion; and children may be beloved for their parents' sake. It gave great joy to the apostle to see children treading in their parents' steps, and likely in their turn to support the gospel. May God bless such families more and more, and raise up many to copy their example. How pleasing the contrast to numbers who spread irreligion, infidelity, and vice, among their children! Our walk is true, our converse right, when according to the word of God. This commandment of mutual Christian love, may be said to be a new one, in respect of its being declared by the Lord Christ; yet, as to the matter, it is old. And this is love to our own souls, that we obey the Divine commands. The foresight of the decay of this love, as well as of other apostacies, or fallings away, might engage the apostle to urge this duty, and this command, frequently and earnestly.
6. "Love is the fulfilling of the law" (Ro 13:10), and the fulfilling of the law is the sure test of love.
This is the commandment—Greek, "The commandment is this," namely, love, in which all God's other commandments are summed up.