God also said He would give us a New Covenant where He would "forgive their wickedness and recognize their sins no more"..
Jesus died for all our sins, past/present/future if we only confess to Him and accept Him as our Savior.
Without His sacrifice, we would all be as doomed as those who broke his laws in the Old Covenant for much "lesser" violations.
What does the New Covenant say is the only unforgivable sin? Is the New Covenant any less believable/valid than the Old Covenant?
I am not going to allow you to change the subject to "unforgivable sins", since it has no bearning on this discussion. This issue was sins and the punishments required for them in this life. Even a saved believer can commit murder and be required to surrender his mortal life (capital punishment).
His eternal disposition is assured, otherwise God was a liar when he promised to forgive the eternal consequence of sin.