Hebrews 9:13

if the blood of bulls and of goats, and the ashes of a heifer sprinkling the unclean The writer has designedly chosen the two most striking sacrifices and ceremonials of the Levitical Law, namely the calf and the goat offered for the sins of people and priest on the Day of Atonement (Leviticus 16) and "the water of separation," or rather "of impurity," i.e. "to remove impurity" "as a sin-offering" described in Numbers 19:1-12 (comp. Hebrews 7:26).

of a heifer The Jews have the interesting legend that ninesuch red heifers had been slain between the time of Moses and the destruction of the Temple.

the unclean Those that have become ceremonially defiled, especially by having touched a corpse.

sanctifieth to the purifying of the flesh i.e. if these things are adequate to restore a man to ceremonial cleanness which was a type of moral purity. So much efficacy they had;they did make the worshipper ceremonially pure before God: their further and deeper efficacy depended on the faith and sincerity with which they were offered, and was derived from the one offering of which they were a type.