Hebrews 9:13 For if the blood of bulls and goats and the ashes of a heifer, sprinkling the unclean, sanctifies for the purifying of the flesh,
The sancitfication mentioned here is ritualistic or ceremonial in nature. That is why the writer expresses it as sancitfication for the purifying of the flesh. It ritually cleanses the body, or symbolizes the spiritual cleansing that all such sacrifices are the antitype of. But specifically, what is the author referring to from the Mosaic Law?