The old system under the law of Moses was only a shadow, a dim preview of the good things to come, not the good things themselves. The sacrifices under that system were repeated again and again, year after year, but they were never able to provide perfect cleansing for those who came to worship.
If they could have provided perfect cleansing, the sacrifices would have stopped, for the worshipers would have been purified once for all time, and their feelings of guilt would have disappeared.
But instead, those sacrifices actually reminded them of their sins year after year.
For it is not possible for the blood of bulls and goats to take away sins.
That is why, when Christ came into the world, he said to God, “You did not want animal sacrifices or sin offerings. But you have given me a body to offer.
References for Hebrews 10:5
You were not pleased with burnt offerings or other offerings for sin.
Then I said, ‘Look, I have come to do your will, O God— as is written about me in the Scriptures.’”
References for Hebrews 10:7
First, Christ said, “You did not want animal sacrifices or sin offerings or burnt offerings or other offerings for sin, nor were you pleased with them” (though they are required by the law of Moses).
Then he said, “Look, I have come to do your will.” He cancels the first covenant in order to put the second into effect.
For God’s will was for us to be made holy by the sacrifice of the body of Jesus Christ, once for all time.