"Beloved: We have this confidence in him that if we ask anything according to his will, he hears us.
And if we know that he hears us in regard to whatever we ask, we know that what we have asked him for is ours. If anyone sees his brother sinning, if the sin is not deadly, he should pray to God and he will give him life. This is only for those whose sin is not deadly. There is such a thing as deadly sin, about which I do not say that you should pray. All wrongdoing is sin, but there is sin that is not deadly.
"We know that anyone begotten by God does not sin; but the one begotten by God he protects, and the Evil One cannot touch him. We know that we belong to God, and the whole world is under the power of the Evil One. We also know that the Son of God has come and has given us discernment to know the one who is true. And we are in the one who is true, in his Son Jesus Christ. He is the true God and eternal life. Children, be on your guard against idols." [1 John 5:14-21]
After his final conclusion to the letter, St John offers a brief summary of the letter’s central theme, which is followed by a kind of appendix that contains a few last recommendations and exhortations to the letter’s readers.
The sacred writer here bolsters peoples’ confidence in prayer and urges the need to pray for sinners. “Mortal” sin (v.16), literally, “sin that leads to death,” reminds us of the sin against the Holy Spirit (see Mt 12:13-32) and that of apostasy (see Heb 6:4-8), “John seems to wish to emphasize the incalculable seriousness of what constitutes the very essence of sin, namely the rejection of God, raising them to the status of idols or false gods” (John Paul II, Reconciliatio et paenitentia, 17).
Although St John makes a point of not saying that these sinners should be prayed for, he does not deny that there is hope for them, given the power and mercy of God. Pope St Gelasius I taught: “There is a sin of death for those who persist in that same sin; there is a sin not of death for those who desist from sin. There is, certainly, no sin for the pardon of which the Church does not pray or from which, by the power which was divinely granted to it, it cannot absolve those who desist from it” (Ne forte).
Jesus Christ, true God and true man, is also eternal life, because only in him can we attain that life. “In this Johannine affirmation there is an indication of hope, based on the divine promises: the Christian has received the guarantee and the necessary strength not to sin” (John Paul II, Reconciliatio et paentitentia, 20). In this closing words, St John appeals to Christians to realize what a great gift it is to be a child of God. As St Leo the Great says, reminding the Christian of his or her dignity, “Think about the head and body of which you now form part. Never forget that you were freed from the power of darkness and led into the light and the Kingdom of God” (Sermo I in Nativitate, 13).