Mark 3:29
But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation:
Cross-reference
Matthew 25:46
Related theme
In Matthew 25:46, 'eternal punishment' parallels the 'eternal sin' here—both describe an unending consequence for the unrighteous.
2 Thessalonians 1:9
Related theme
In 2 Thessalonians 1:9, 'eternal destruction' and separation from God match the unforgivable, eternal nature of the sin mentioned here.
Leviticus 24:16
Historical context
In Leviticus 24:16, blasphemy against God's name carries the death penalty—showing the OT background of severe punishment for blasphemy, now intensified to eternal sin.
Matthew 12:32
Parallel
In Matthew 12:32, the same teaching appears: speaking against the Holy Spirit is unforgivable—a direct parallel of this verse.
Luke 12:10
Parallel
Luke 12:10 parallels this but adds that speaking against the Son of Man can be forgiven, contrasting with blasphemy against the Spirit.