I grew up in the largest cow town in America, but I’m still essentially a city boy. So I had to ask what a red heifer would be. The word has two elements, in the Bible. First, a heifer is a young female cow (don’t blame me; that’s how the New Oxford American Dictionary said it!) that has not born a calf. The second element is clear from Numbers 19.2: “on which no yoke has ever come.” The animal, finally, had to be red, having red hair. In later Jewish practice, the animal had to have no more than two black hairs growing out of the same follicle. Recently, in 1999, Israel thought that a valid red heifer had been born in the country, but later it was disqualified (I did not hear the reason for the disqualification).
The law required that the priesthood burn the animal completely to ash. They then gathered the ash and preserved it for important cleansing rituals (explained in Num 19.11-22). Ritual purity was the presupposition of the entire Law of Moses. This ritual purity concerned matters, generally, such as physical conditions (childbirth, for example), but especially physical contact with death. This is the particular concern in Numbers 19. There are, then, two types of impurity: minor impurities that do not require sacrificial remedies, and major impurities that require sacrifice (as in Lev 14, the ritual for purifying someone who has had leprosy). The chief impurity is death. Contracting the impurity of death threatened severing the Israelite from his people (Num 19.20). So, going through the ritual of the red heifer made one fit to participate in the public worship of God.
If these things are true, Hebrews 9.13-14 says, then it is all the more true that one who is clean because of the blood of Christ is fit for the worship of God. Our problem, then, becomes a problem of faith, not one of sin. Is the blood of Christ more powerful than my sin? Is it more powerful and authoritative than my conscience? If not, then we really are not fit for the service of God. If so, then no amount of grieving is needed. No amount of pleading is needed. Only the blood of Christ satisfies God. Or else, my conscience is more righteous, powerful, holy, than God is.