Hebrews 9:6-10 (ESV)
These preparations having thus been made, the priests go regularly into the first section, performing their ritual duties,  but into the second only the high priest goes, and he but once a year, and not without taking blood, which he offers for himself and for the unintentional sins of the people.  By this the Holy Spirit indicates that the way into the holy places is not yet opened as long as the first section is still standing  (which is symbolic for the present age). According to this arrangement, gifts and sacrifices are offered that cannot perfect the conscience of the worshiper,  but deal only with food and drink and various washings, regulations for the body imposed until the time of reformation.
“According to this arrangement, gifts and sacrifices are offered that cannot perfect the conscience of the worshiper.” Cannot perfect the conscience of the worshiper. Of course this phrase is setting up for something to come, it is a comparison. The author is saying that all the Old Testament practices were pretty much futile, they were mere regulations imposed until the time of the reformation. That is until the time that Christ had died on the cross, a sacrifice unlike the old sacrifices in that this one does perfect the conscience of the worshiper. Christ perfects your conscience. Your conscience is perfect by virtue of his sacrifice, which means anything you try to do to perfect it only goes to blemish it.