In this second portion of 1 John 2, John begins to turn his attention to the way Christ lived and what that means for us. The command to love one another (and the consequences for failing to do so) dominate this section. Through it all, the focus remains, however, on fellowship: fellowship first with God through Christ, and second by expressing (and indeed living out) that fellowship by keeping Christ’s command to “love one another.”
v7. Next, John points out that what he is saying is “not an new command, but an old one.” That is, this is something that the church had always known. In fact, they “have had it since the beginning.” So what is this “old command.” John says it “is the message you have heard.” That message, of course, is in general the gospel of Jesus Christ, and in particular Jesus’ command that we “love one another.” That is how He lived, what He commanded us to do, and how we are likewise to live.