Jesus believed that blasphemy (speaking sacrilegiously about God or sacred things) was forgivable, with only one exception:
All manner of blasphemies shall be forgiven. Whoever speaks against the Son of Man shall be forgiven. But he that blasphemes against the Holy Spirit will never be forgiven, and is in danger of eternal damnation.
This is in contrast to the Law of Moses, which prescribes strict belief in the Jewish God, requiring belief that God exists and is unique, abstinence from blasphemy, hallowing God’s name, loving God, fearing God, and not putting the word of God to the test.
Why does Jesus say that blasphemy (against both God and Jesus’s exalted form, the Son of Man) is forgivable, and why the one prohibition, the “Unpardonable Sin”? I believe that he is saying that belief in a higher power, the Holy Spirit or Paul’s God who is Love, is the one belief that is essential if you are to enter the kingdom of heaven.