A.T. Robertson Commentary Mark 3:29

"but whosoever shall blaspheme against the Holy Spirit hath never forgiveness, but is guilty of an eternal sin:" — Mark 3:29 (ASV)

Guilty of an eternal sin (ενοχος εστιν αιωνιου αμαρτηματος). The genitive of the penalty occurs here with ενοχος. In saying that Jesus had an unclean spirit (verse 30) they had attributed to the devil the work of the Holy Spirit. This is the unpardonable sin and it can be committed today by men who call the work of Christ the work of the devil, Nietzsche may be cited as an instance in point. Those who hope for a second probation hereafter may ponder carefully how a soul that eternally sins in such an environment can ever repent. That is eternal punishment. The text here is αμαρτηματος (sin), not κρισεως (judgment), as the Textus Receptus has it.