What is the 'sin unto death' in 1 John 5:16, and is it blasphemy against the Holy Spirit?
A viewer asks whether Romans 6:16 and 1 John 5:16 (the sin unto death) are a warning about losing one's justification or salvation, and what the sin unto death actually is.
Answer
Romans 6:16 is not the sin unto death; it simply says you are slaves of the one you obey, either sin leading to death or obedience leading to righteousness. The sin unto death is in 1 John 5:16, where John mentions almost as an afterthought that there is a sin that is mortal, a sin unto death, for which he does not even say to pray. That sin is unforgivable, so it must be serious, and we find it in the Gospels, Matthew 12 and Mark 3, where the Pharisees see Jesus perform stupendous miracles, raising the dead and restoring limbs, things only God's creative power can do, and instead of bowing the knee they say he casts out devils by Beelzebul. Now, Jesus performed those miracles by the power of the Holy Spirit, because in his humanity he depended on the Spirit; so to say he does them by the devil is to blaspheme the Holy Spirit, calling the Spirit the devil. That is the unforgivable sin, directly speaking. It is not merely giving up the faith; someone can lose faith for a time and come back. It is the deliberate, hardened decision, like the Pharisees, to invent a lie so as not to bow to who Jesus really is, and to attribute the work of the Holy Spirit to Satan. That is crossing the line, the point of no return.