Just as New Testament grace should not be used as a license for deliberate sin (Romans 6) but was intended for unintentional sins to empower Jesus' followers trying to walk the narrow way that leads to life, the animal sacrifices in the Old Testament were also intended to atone for the people's unintentional sins according to
Hebrews 9:7:
"but into the second only the high priest goes, and he but once a year, and not without taking blood, which he offers for himself and
for the unintentional sins of the people."
This is in reference to passages such as Numbers 15:30-31 (NLT)
“
But those who brazenly violate the Lord’s will, whether native-born Israelites or foreigners, have blasphemed the Lord, and they must be cut off from the community.
Since they have treated the Lord’s word with contempt and deliberately disobeyed his command, they must be completely cut off and suffer the punishment for their guilt.”
So Hebrews 10:26-31 in this context is not referring to Jews who went back to the law but believers who are abusing the grace of God and using it as an excuse to "deliberately sin". Willful sin such as murder and adultery resulted in stoning in the law of Moses and the writer of Hebrews is saying how worse a punishment there will be for false Christians who use grace as a license to sin since they are profaning not the blood of animals, but the blood of Jesus Christ.
Hebrews 10:26-31
"For if we go on
sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, but a fearful expectation of judgment, and a fury of fire that will consume the adversaries.
Anyone who has set aside the law of Moses dies without mercy on the evidence of two or three witnesses. How much worse punishment, do you think, will be deserved by the one who has trampled underfoot the Son of God, and has
profaned the blood of the covenant by which he was sanctified, and has outraged the Spirit of grace? For we know him who said, “Vengeance is mine; I will repay.” And again, “The Lord will judge his people.” 31 It is a fearful thing to fall into the hands of the living God."
In his letter to the churches, Jesus has a strong rebuke for the Nicolaitans. The Nicolaitans adhered to the Nicene creed like we all do but they taught that God's grace allowed them to live immoral lives for pleasure. Their heart was not circumcised so they were not spiritual Jews.
https://www.samstorms.org/enjoying-g...he-nicolaitans