Hebrews 9:13

For if the blood of goats and bulls, and a [burnt] heifer's ashes sprinkled on people who had been [ceremonially] defiled, could purify them so as to make them [ceremonially] clean on the outside,

2 Corinthians 5:21

God considered Christ to be sinful on our behalf, even though He never sinned, so that we could be considered right with God through Him.

2 Corinthians 7:1

[So], since we have these promises [See 6:16-18], dear ones, we should purify ourselves from everything that pollutes [our] body and spirit while living lives completely separated [from sin], out of reverence for God.

Hebrews 7:26

For Jesus was a very suitable head priest for us [i.e., He meets our needs very well], because He was holy, innocent, without [moral] corruption, separated from sinners and [exalted] above the heavens.

Treasury of Scripture Knowledge

Summary

And a man that is clean shall gather up the ashes of the heifer, and lay them up without the camp in a clean place, and it shall be kept for the congregation of the children of Israel for a water of separation: it is a purification for sin.

A water of separation

Bible References

Clean

2 Corinthians 5:21
God considered Christ to be sinful on our behalf, even though He never sinned, so that we could be considered right with God through Him.
Hebrews 7:26
For Jesus was a very suitable head priest for us [i.e., He meets our needs very well], because He was holy, innocent, without [moral] corruption, separated from sinners and [exalted] above the heavens.
Hebrews 9:13
For if the blood of goats and bulls, and a [burnt] heifer's ashes sprinkled on people who had been [ceremonially] defiled, could purify them so as to make them [ceremonially] clean on the outside,

A water of separation

2 Corinthians 7:1
[So], since we have these promises [See 6:16-18], dear ones, we should purify ourselves from everything that pollutes [our] body and spirit while living lives completely separated [from sin], out of reverence for God.