“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.”
King James Version (KJV)
5:16 This extends to things of the greatest importance. If any one see his brother - That is. any man. Sin a sin which is not unto death - That is, any sin but total apostasy from both the power and form of godliness. Let him ask, and God will give him life - Pardon and spiritual life, for that sinner. There is a sin unto death: I do not say that he shall pray for that - That is, let him not pray for it. A sin unto death may likewise mean, one which God has determined to punish with death.
1Jo 5:16 If a man see his brother sin a sin. Then a brother can be overtaken by sin. Not unto death. There is a sin not unto death, and one unto death. The sin described in Heb 6:4-6 is evidently unto death; that described in Ga 6:1 is one not unto death. In the latter case the sinners can be restored, and we may pray for them with the assurance that they will be. This implies both work and prayer.