the same shall purify himself therewith on the third day, and on the seventh day he shall be clean: but if he purify not himself the third day, then the seventh day he shall not be clean.

Shall be sprinkled with this water on the third day, and on the seventh, and so shall be cleansed. If he were not sprinkled on the third day, he cannot be cleansed on the seventh.

he doth cleanse himself for it on the third day, and on the seventh day he is clean; and if he cleanse not himself on the third day, then on the seventh day he is not clean.

On the third day and on the seventh day he is to make himself clean with the water, and so he will be clean: but if he does not do this on the third day and on the seventh day, he will not be clean.

the same shall purify himself therewith on the third day and on the seventh day, and he shall be clean; but if he purify not himself the third day and the seventh day, he shall not be clean.

shall be sprinkled from this water on the third and seventh days, and so shall he be cleansed. But if he was not sprinkled on the third day, he is not able to be cleansed on the seventh.

Ipse purificabitur eo die tertia, et die septima mundus erit: quod si non purificatus fuerit die tertia, die septima non erit mundus.

He shall purify himself with it - יתחטא בו yithchatta bo, literally, he shall sin himself with it. This Hebrew form of speech is common enough among us in other matters. Thus to fleece, to bark, and to skin, do not signify to add a fleece, another bark, or a skin, but to take one away; therefore, to sin himself, in the Hebrew idiom, is not to add sin, but to take it away, to purify. The verb חטא chata signifies to miss the mark, to sin, to purify from sin, and to make a sin-offering. See the note on Genesis 13:13.
The Hebrews generally sacrificed males, no matter of what color; but here a heifer, and a heifer of a red color, is ordered. The reason of these circumstances is not very well known.
"The rabbins, with all their boldness," says Calmet, "who stick at nothing when it is necessary to explain what they do not understand, declare that the cause of this law is entirely unknown; and that Solomon, with all his wisdom, could not find it out."
Several fathers, as well modern as ancient, profess to understand the whole clearly.
1. The red heifer with them signifies the flesh of our Lord, formed out of an earthly substance.
2. Being without spot, etc., the infinite holiness of Christ.
3. The sex of the animal, the infirmity of our flesh, with which he clothed himself.
4. The red color, his passion.
5. Being unyoked, his being righteous in all his conduct, and never under the yoke of sin.
6. Eleazar's sacrificing the heifer instead of Aaron, Genesis 13:3, signifies the change of the priesthood from the family of Aaron, in order that a new and more perfect priesthood might take place.
7. The red heifer being taken without the camp (Genesis 13:3) to be slain, points out the crucifixion of our Lord without the city.
8. The complete consuming of the heifer by fire, the complete offering of the whole body and soul of Christ as a sacrifice to God for the sin of man: for as the heifer was without blemish, the whole might be offered to God; and as Christ was immaculate, his whole body and soul were made a sacrifice for sin.
9. As the fire of this sacrifice ascended up to God, so it points out the resurrection and ascension of our blessed Lord.
10. And as the ashes of this victim communicated a legal purity to those who were defiled, so true repentance, signified by those ashes, is necessary for the expiation of the offenses committed after baptism.
A great part of this is true in itself; but how little evidence is there that all these things were intended in the ordinance of the red heifer? See on Numbers 8:7 (note).

He shall purify himself (f) with it on the third day, and on the seventh day he shall be clean: but if he purify not himself the third day, then the seventh day he shall not be clean.
(f) With the sprinkling of water.

He shall purify himself with it,.... That is, with the ashes of the water of purification made of them: and this was to be done first
on the third day; from the time of his touching the dead body. Aben Ezra intimates, that there is a secret or mystery in this and the following number seven; it may respect the third day of Christ's resurrection, who, as he shed his blood for the expiation and purification of sinners, so he rose again the third day for the justification of them:
and on the seventh day he shall be clean; which may denote the perfect state, or sabbath of rest, which remains for the people of God, when all Christ's purified and justified ones shall be clear of all sin, and be the spirits of just men made perfect:
but if he purify not himself the third day, then the seventh day he shall not be clean; whoever is not cleansed from his sins by the blood of Christ, shed for the remission of them, and is not justified from them by him that rose from the dead the third day, will never be cleansed in the world to come, or in the eternal sabbath; but it will then be said, "let him that is filthy be filthy still", Revelation 22:11.

He shall purify himself . . . the third day--The necessity of applying the water on the third day is inexplicable on any natural or moral ground; and, therefore, the regulation has been generally supposed to have had a typical reference to the resurrection, on that day, of Christ, by whom His people are sanctified; while the process of ceremonial purification being extended over seven days, was intended to show that sanctification is progressive and incomplete till the arrival of the eternal Sabbath. Every one knowingly and presumptuously neglecting to have himself sprinkled with this water was guilty of an offense which was punished by excommunication.

With it - With the water of separation. On the third day - To typify Christ's resurrection on that day by which we are cleansed or sanctified.