Hebrews 10:8-10 (ESV)
When he said above, “You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings” (these are offered according to the law), then he added, “Behold, I have come to do your will.” He does away with the first in order to establish the second. And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.
The context of the above passage matters to understand what the writer is saying in these verses. The writer has been making the case that Jesus is both the fulfillment of the old sacrificial system of bulls and goats and is a better and final sacrifice. That has been the subject of the first nine chapters. In the above verses the writer tells us the advantage of that for us. Since the old system had to be done every year, the purity of the people demanded they come every year and make those sacrifices of bulls and goats. But, as stated above, when Jesus came to fulfill the will of His Father, He did away with coming year after and year and once for all provided purity (sanctification) for those who come to Him, by faith. His own body sacrifice was the end of all sacrifices and became our path to purity in Him. We can rejoice that we don’t need to come and sacrifice and offer and confess over and over and over. He did this once for all, and established our forever sanctification.