5:20. And we know that the Son of God is come. And he hath given us understanding that we may know the true God and may be in his true Son. This is the true God and life eternal. And may be in his true Son. He is, or this is the true God, and life eternal... Which words are a clear proof of Christ's divinity, and as such made use of by the ancient fathers. 5:21. Little children, keep yourselves from idols. Amen. Keep yourselves from idols... An admonition to the newly converted Christians, lest conversing with heathens and idolaters, they might fall back into the sin of idolatry, which may be the sin unto death here mentioned by St. John.