John Gill, on Heb 9:13

For if the blood of bulls and of goats,.... Shed either on the day of atonement, or at any other time: the former of thee, Pausanias (y) relates, was drank by certain priestesses among the Grecians, whereby they were tried, whether they spoke truth or no if not, they were immediately punished; and the latter, he says (z), will dissolve an adamant stone; but neither of them can purge from sin: and the ashes of an heifer sprinkling the unclean; the apostle refers to the red heifer, Num 19:1 which being burnt, its ashes were gathered up and put into a vessel, and water poured upon them, which was sprinkled with a bunch of hyssop on unclean persons; the ashes and the water mixed together made the water of separation, or of sprinkling; for so it is called by the Septuagint, "the water of sprinkling", and in the Targum in a following citation: this was the purification for sin, though it only sanctifieth to the purifying of the flesh; the body, or only in an external and typical way, but did not really sanctify the heart, or purify and cleanse the soul from sin. The Jews say, that the waters of purification for sin were not waters of purification for sin, without the ashes (a); and to this the Targumist, on Eze 36:25 and on Zac 13:1 refers, paraphrasing both texts thus; "I will forgive their sins as they are cleansed with the water of sprinkling, and with the ashes of the heifer, which is a purification for sin.'' (y) Achaica, sive l. 7. p. 450. (z) Arcadica, sive l. 8. p. 485. (a) Misn. Temura, c. 1. sect. 5. Maimon. & Bartenora in ib.