Matthew Henry Commentary 2 John 1:4-6

"I rejoice greatly that I have found [certain] of thy children walking in truth, even as we received commandment from the Father. And now I beseech thee, lady, not as though I wrote to thee a new commandment, but that which we had from the beginning, that we love one another. And this is love, that we should walk after his commandments. This is the commandment, even as ye heard from the beginning, that ye should walk in it." — 2 John 1:4-6 (ASV)

It is good to be trained in faith from an early age; and children may be beloved for their parents' sake. It gave great joy to the apostle to see children following in their parents' footsteps, and likely, in 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 those who spread irreligion, infidelity, and vice among their children!

Our walk is true and our conduct right when they are in accordance with the Word of God. This commandment of mutual Christian love may be called new in that it was declared by the Lord Christ; yet, in its substance, 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 apostasies, or fallings away, might have prompted the apostle to urge this duty and this command frequently and earnestly.