Hebrews 7:19
7:19 for the law made nothing perfect. On the other hand a better hope is introduced, through which we draw near to God.
Hebrews 7:28
7:28 For the law appoints as high priests men subject to weakness, 1 but the word of solemn affirmation that came after the law appoints a son made perfect forever.
Hebrews 9:9
9:9 This was a symbol for the time then present, when gifts and sacrifices were offered that could not perfect the conscience of the worshiper.
1 sn See Heb 5:2 where this concept was introduced.