John Wesley on 1 John 5:20

And we know - By all these infallible proofs. That the Son of God is come - Into the world. And he hath given us a spiritual understanding, that we may know him, the true one - "The faithful and true witness." And we are in the true one - As branches in the vine, even in Jesus Christ, the eternal Son of God. This Jesus is the only living and true God, together with the father and the Spirit, and the original fountain of eternal life. So the beginning and the end of the epistle agree.