1. Mark 3:29 (ESV)
  2. Exposition

Why does Jesus add that someone who blasphemes against the Holy Spirit is guilty of an eternal sin?

Mark 3:29 (ESV)

29 but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin”

With these words Jesus is actually warning the scribes. He is warning them that they are in danger of eternal damnation because of their refusal to repent and believe in him. They are words of warning from Jesus. They are not a condemnation by Jesus.