Numbers 19:9

And a man [that is] clean shall gather up the ashes of the
heifer
A man, a clean priest, as the Targum of Jonathan; in later times great care was taken that the priest concerned in the burning of the red cow should be pure; he was separated from his own house seven days before the time, and every day he was sprinkled with the blood of all sin offerings then offered, that it might be sure he was free from any pollution by a grave, or a dead body; and for the same reason they made a causeway on double arches from the temple to the mount of Olives, over the valley of Kidron, lest any unseen grave should be in the way; and when he came thither he was obliged to wash or dip himself, as before observed ^F13; and so he that gathered up the ashes was to be clean from all ceremonial pollution: the Jews say ^F14, that they pounded the ashes; if there were any black coal in them or bone, they did not leave it in them, but sifted them in stone sieves; and not the ashes of the heifer only they took, but the ashes of the cedar wood mixed with them; and these they put, as the Targum of Jonathan says, into an earthen vessel enclosed in a covering of clay:

and lay [them] up without the camp in a clean place;
they were divided into three parts, according to the Targum of Jonathan, one part was put in the Chel (or the enclosure of the court of the tabernacle), another in the mount of Olives, and the third part was divided among all the wards of the Levites, with which the Misnah ^F15 agrees; Jarchi makes mention of the same division, and of the use of each; that the wards had was without the court, that the citizens might take of it, and all that needed to be purified; that in the mount of Olives was for the priests, to sanctify other heifers with it; and that in the Chel was for a reserve:

and it shall be kept [for a reserve] for the congregation of Israel;
as ashes may be kept a long time, if well taken care of, because they are not subject to any corruption or putrefaction; and so was, as Bishop Patrick observes from Dr. Jackson, a figure of the everlasting efficacy of Christ's blood: and, according to the Jews, these ashes of the first heifer must last more than a thousand years; for they say ^F16 the second that was burnt was in the time of Ezra, though they reckon seven more afterwards before the destruction of the second temple, in all nine; and the tenth they expect in the days of the Messiah, which are past; he, being come, has put an end to this type by fulfilling it in himself: and the use of them was

for a water of separation;
being put into water, and mixed with it, was for the cleansing of such as were separated from others for their uncleanness, and was a purification of them for it, as follows:

it [is] a purification for sin:
or "it [is] sin" ^F17, not an offering for sin, properly speaking; the heifer, whose ashes they were, not being sacrificed in the tabernacle, nor on the altar, and wanted other rites; yet it answered the purposes of a sin offering, and its ashes in water were typical of the blood of Christ, which purges the conscience from dead works, when this only purified to the sanctifying of the flesh, ( Hebrews 9:13 Hebrews 9:14 ) ; and is the fountain set open for sin and uncleanness, ( Zechariah 13:1 ) ; where both the words are used which are here, and in the preceding clause: ashes are known to be of a cleansing nature, and so a fit emblem of spiritual purification by Christ; and the duration of them of the perpetuity of it.