If any man, &c. As if he had said, Yea, he hears us not only for ourselves, but others also; see his brother That is, any child of man; sin a sin which is not unto death That is, any sin but that which is marked out in the awful words of our Lord Jesus Christ as unpardonable, namely, the blasphemy against the Holy Ghost, of which see on Matthew 12:31; Mark 3:29. Or, which may rather be intended, the sin of total apostacy from both the power and form of godliness; he shall ask, and God shall give him life Repentance unto life, and, in consequence thereof, pardon and salvation for that sinner. There is a sin unto death; I do not say that he shall pray for it That is, let him not pray for it. A sin unto death may likewise mean one which God has determined to punish with temporal death. All unrighteousness is sin Every deviation from perfect holiness is sin; but all sin is not unpardonable, nor does God determine to punish every sin with temporal death.
Related Commentaries of 1 John 5:16
1 John 5:16-17
16 If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
17 All unrighteousness is sin: and there is a sin not unto death.