And every priest stands ministering daily and offering repeatedly the same sacrifices, which can never take away sins.  (12) But this Man, after He had offered one sacrifice for sins forever, sat down at the right hand of God, (13) from that time waiting till His enemies are made His footstool.  (14) For by one offering He has perfected forever those who are being sanctified. (18) Now where there is remission of these, there is no longer an offering for sin.

In the sacrifice of Christ Jesus, God promises He will remember our sins no more. In Christ believers receive total forgiveness – the righteousness of Christ is imputed to believers.  The law of Moses of the Old Testament could never have done that.  This is the main argument in the letter to the Hebrews; converted Jews should not revert to the Jewish system to escape persecution. In the Jewish system there is no complete forgiveness and no access to God except through Christ Jesus. Why would any man/woman forfeit this??

Our verses today illustrate the totality of our forgiveness for sin by contrasting the unfinished, repetitive ministry of the Old Testament priests with the once and for all saving sacrifice of Christ at the cross.  Old Testament sacrifices could never take away sin and they are now worthless and obsolete. Through the cross, in Christ, we have total forgiveness – why would anyone dare risk reverting to a system that cannot do that?