{I was very glad} because I found [some] of your children walking in [the] truth, just as {the Father commanded us}.

And now, dear lady, I pray you--writing to you, as I do, not a new command, but the one which we have had from the very beginning--let us love one another.

The love of which I am speaking consists in our living in obedience to God's commands. God's command is that you should live in obedience to what you all heard from the very beginning.