But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.

But the person who obeys what His teaching requires, truly in this person love for God has been made complete. This is [another way] to be sure that we are in [fellowship with] Him:

My dearly loved ones, I am not writing to you about a new commandment, but about an old one. [It is the one] you had learned about from the beginning. [Note: This is the commandment to love one another (3:1: II John 5) which Jesus had taught his disciples during His earthly ministry. See Mark 12:31]. This old commandment is the word [of God] which you heard [previously].

Yet, I am [also] writing to you about a new commandment [Note: This commandment was to love one another as Jesus loved them. See John 13:34]; its truth is [being demonstrated] by Christ [perfectly] and [also] by you people [in a lesser measure], because the darkness [of sin] is passing away, and the real light [of righteousness] is already shining [in people's lives].

You people should continue [to practice] what you heard from the beginning [i.e., to love one another, See verses 7-11]. If you do, then you also will continue in [fellowship with] the Son, and with the Father.

For this is the message that ye heard from the beginning, that we should love one another.

We know that we have passed from death to life, because we love one another. The person who does not love remains spiritually dead.

And this is his commandment, That we should believe on the name of his Son Jesus Christ, and love one another, as he gave us commandment.

And God lives in the heart of the person who [continually] obeys His commands, and he lives in [fellowship with] God. And here is [another] way we know that God lives in our hearts: It is by [means of] the Holy Spirit, whom God gave to us. [See Rom. 8:9, 11; James 4:5; I Cor. 6:19].

Beloved, let us love one another: for love is of God; and every one that loveth is born of God, and knoweth God.

Beloved, if God so loved us, we ought also to love one another.

No man hath seen God at any time. If we love one another, God dwelleth in us, and his love is perfected in us.