What is the ‘sin unto death’ mentioned in 1 John 5:16?

This text is from a transcript of a talk by David Gooding, entitled ‘Unity, Origin and Victory’ (1987).

As far as I know, three suggestions have been made. First, the one based upon such passages as 1 Corinthians 11:31–32, which says of believers that 'if we would judge ourselves, we should not be judged, but when we are judged, we're chastened of the Lord so that we should not be condemned with the world.' 'For this cause,' says Paul, 'many are weak and sickly among you and some have fallen on sleep' (1 Corinthians 11:30) meaning, presumably, under the discipline of God. If as believers we do not discern ourselves and we do not judge ourselves and we go on living carelessly, then the Lord will deal with us. Every time we take the cup of the Lord at the Lord's Supper, we are taking the cup of a covenant whereby our Lord guarantees and pledges himself that he will write God's laws on our heart.

Now normally he does that with our cooperation, as we judge ourselves and confess our sin and seek his grace to overcome it. But if we grow careless then the Lord will take us in hand. He pledged to do it so that we shall not be condemned with the world. If it is so that a believer has so misbehaved that the Lord has decided in his case he must take him home—better for all concerned, better for the testimony, better for the church he's in, better for his family—then there's a sense in which, whatever you say, the Lord won't listen to your prayers. 'I don't say that you should pray for such a one,' says John (1 John 5:16). But there are other cases where the Lord might be disciplining his people and is prepared to listen to the intercessions of some godly friend of theirs, like he listened to Abraham's intercessions and spared Lot from destruction in the city of Sodom. That's one explanation then.

Others have thought that the sin unto death is not just when a believer has sinned grievously and the Lord has decided to take him home, but it is talking about the unpardonable sin. Somebody has committed a sin and there is no possibility of renewing such a one to repentance, and therefore you waste your breath if you try to pray for them. Well I suppose it could mean that. I think the difficulty is going to be when you come to the other side. Those that don't sin unto death, then: who are they who nonetheless need life given them? For the question is praying for those who have sinned, but have not sinned unto death—in what sense therefore do they need life?

In my own thinking, someone that, in the sense of Hebrew 6:4, who, having tasted of the heavenly gift falls aside, I think that passage is talking of apostates, and in my book I don't think apostates were ever true believers at all. They were like the men of whom we read in 1 John 2:19: 'they went out from us because they were not of us. They never were.' They made a profession, but it wasn't real. They were illuminated, but they never did repent or believe. They were never born again. With their eyes open, they have turned away from the gospel. You won't renew them again to repentance even if you try. You'll never get them to change their minds.

Some have said a third case; that this is talking about the ordinary, unconverted person who, while he goes on sinning, has not yet rejected the gospel knowingly with his eyes open and that, if you pray for him, God will give you life. That is, he'll bring the man to conversion. But of course, if it's a case of a person who, having heard the gospel and had his eyes opened and has knowingly rejected it, they have committed then the unpardonable sin. Of those three, the one that seems to me to be better is the first one.

Is there such thing as 'the' unpardonable sin (see Matthew 12:22–37)?

Well, in the place you quote, our Lord did a miracle in the power of the Holy Spirit; and his enemies, at least some of them, didn't deny that it was a supernatural power. They couldn't deny it. There was the evidence straight in front of their eyes. They couldn't deny the miracle had taken place, but they were so determined not to believe that Jesus was the Messiah that they were prepared to attribute that miracle to the devil. And our Lord takes the occasion to argue with them and to show them that they are being deliberately and utterly perverse. In maintaining that he was of the devil, they were contradicting every axiom of thought and behaviour that they would normally apply. They were being knowingly and deliberately and utterly perverse.

I take it that if a man has his eyes opened like that and can see that this is a supernatural power, that this is the Holy Spirit, but is determined not to give in and therefore says that the Holy Spirit is the devil, then what else has God got left with which to convince the man? There comes a point, doesn't there, when God has given all he can give? The last evidence God has got to give is his Holy Spirit, directly illuminating the mind of a man or woman. When God has done that, if the person says 'no', what has God got left with which to bring them to repentance anyway? That is a very solemn thought. It is possible for God to show himself to a man or woman who finally say 'no' and go their way. I myself would think that, whether in our Lord's lifetime or subsequently, unpardonable sins—sins for which there can be no repentance—are sins of that order.