Jamieson, Fausset and Brown on Hebrews 10:4

4. For, &c.--reason why, necessarily, there is a continually recurring "remembrance of sins" in the legal sacrifices (He 10:3). Typically, "the blood of bulls," &c., sacrificed, had power; but it was only in virtue of the power of the one real antitypical sacrifice of Christ; they had no power in themselves; they were not the instrument of perfect vicarious atonement, but an exhibition of the need of it, suggesting to the faithful Israelite the sure hope of coming redemption, according to God's promise.

take away--"take off." The Greek, He 10:11, is stronger, explaining the weaker word here, "take away utterly." The blood of beasts could not take away the sin of man. A MAN must do that (see on He 9:12-14).