All unrighteousness is sin: and there is a sin not unto death.
Every "unrighteousness (even that of believers, cf. 1 John 1:9; 1 John 3:4: coming short of right) is sin;" (but) not every sin is that unto death.
There is a sin not unto death - in the case of which believers may intercede. Death and life stand in correlative opposition (1 John 5:11-13). The sin unto death must be one tending 'toward' х pros (G4314)], so resulting in, death. Alford makes it an appreciable ACT, the denying Jesus to be the Christ, the Son of God (in contrast to confessing it, 1 John 5:1; 1 John 5:5; 1 John 2:19; 1 John 2:22; 1 John 4:2-3; 1 John 5:10). Such willful deniers of Christ are not to be received into one's house, or wished "God speed" (2 John 1:10-11). Still, the state of apostasy accompanying the act is included-a 'state of soul in which faith, love, and hope the new life, is extinguished. The chief commandment is faith and love, which imply life. Therefore, the chief sin is that by which faith and love are destroyed, death. As long as it is not evident ("see," 1 John 5:16) that it is a sin unto death, it in lawful to pray. But when it is a palpable rejection of grace, and the man puts from him life, how can others procure for him life?' Contrast James 5:14-18. Compare Matthew 12:31-32, as to the obstinate rejection of the Holy Spirit's plain testimony to the Divine Messiah. Jesus, on the Cross, pleaded only for those who KNEW NOT what they were doing in crucifying Him; not for those willfully resisting grace (Luke 23:34). If we pray for the impenitent, it must be with humble submission to God's will; not with the intercessory request which we should offer for a brother when erring.