John Gill Commentary Hebrews 10:9

"then hath he said, Lo, I am come to do thy will. He taketh away the first, that he may establish the second." — Hebrews 10:9 (ASV)

Then said he, [lo], I come to do your will, O God
(See Gill on Hebrews 10:7)

he takes away the first, that he may establish the second;

The sense is, either that God has taken away, and abolished the law, that he might establish the Gospel; or he has caused the first covenant to vanish away, that place might be found for the second, or new covenant; or he has changed and abrogated the priesthood of Aaron, that he might confirm the unchangeable priesthood of Christ.

Or rather he has taken away that which was first spoken of in the above citation, namely, sacrifice, offering, burnt offerings, and sin offerings; these he has removed and rejected as insignificant and useless, that he might establish what is mentioned in the second place; namely, the will of God, which is no other than the sacrifice of Christ, offered up according to the will of God, and by which his will is done.