Hebrews 9:13-14 is an example of arguing from lesser to greater:
For if the blood of goats and calves, and ashes of a heifer sprinkling those who have become unclean, sanctifies for the purification of the flesh, how much more will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, purify our conscience from dead works in order to serve the living God!
If the blood of animals could sanctify our flesh, how much more does the blood of Christ cleanse our conscience! If something lesser did that, then something greater does this.
The argument itself is clear enough. But the question we must always ask when reading Hebrews is, Which Mosaic rite does the author have in mind when he writes this? There is only one cleansing rite (near as I can find) that involves sprinkling the ashes of an animal, and that is the rite in Numbers 19. I’ll quote it, compare it to Hebrews 9, and then comment. While the book of Numbers was composed in Hebrew, I’ve included words from the Septuagint translation that correspond to some of the Greek terms that come up in Hebrews 9:
This is the instruction when a man has died in a tent: everyone who comes into the tent and everyone who is in the tent shall be unclean (AKATHARTA) seven days. And every vessel that was open, that had no lid tied on it, it is unclean (AKATHARTA). And everyone who, in the open field, touches someone who was slain with the sword or someone who is dead (NEKROU), or the bone of a man or a grave, shall be unclean (AKATHARTOS) seven days. And for the unclean person (AKATHARTW) they shall take from the ashes (SPODIAS) of the burnt sin offering and add with it living water into a vessel. And a clean (KATHAROS) man shall take hyssop and dip it into the water and sprinkle (PERIRRAVEI) it on the tent and on all the vessels and on the people (literally “souls”) who are there and on the one who touched the bone or the slain or the dead or the grave. And the clean (KATHAROS) shall sprinkle (PERIRRANEI) the unclean (AKATHARTON) on the third day and on the seventh day. And he shall purify him on the seventh day, and he shall wash his garments and bathe himself in water, and he will be clean at evening. (Numbers 19:14-19).
Thus in Hebrews 9 we have the SPODOS ‘ashes’ of the heifer. Those ashes sprinkle the defiled persons. The word for sprinkling in Hebrews 9 is RHANTIZOUSA, from RHANTIZW. This is related to the word in the Septuagint in Numbers 19, PERIRRAINW, a combination of the preposition PERI ‘around’ and RHAINW ‘sprinkle.’ The ashes sprinkle for the purification of the flesh, the word for ‘purification’ being KATHAROTHTA. It says in Hebrews 9 that the blood of Christ likewise will cleanse, KATHARIEI. But whereas the ashes of the heifer sprinkle to purify the flesh from death, the blood of Christ sprinkles us in order to purify our conscience from dead works (NEKRWN ERGWN).
And what does this Mosaic rite have to do with the life of a Christian? First of all, just as the sprinkling ashes referred to an actual sprinkling with ashes in Numbers 19, so also the sprinkling of the blood of Christ is not an inward, spiritual thing, but is likewise an actual outward sprinkling. This literal sprinkling happens in Holy Baptism.
As it is in Hebrews 9, so elsewhere the good conscience is connected with Baptism. For example in 1 Peter 3:21 Baptism is called “an appeal to God for a good conscience.” Similarly in Hebrews 10:22, “our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.” The sprinkling of the heart and the washing of the body are one and the same: through the outward washing of Holy Baptism God deals with us inwardly and cleanses our heart.
And make no mistake, this sprinkling with the blood of Christ did not merely happen once in Baptism, a long time ago, never to happen again. No, we are baptized, present tense, and the sprinkling of Christ’s blood continues all our days, so long as faith exists to receive it. Therefore our conscience is constantly cleansed from dead works through Baptism.
Second, while we’re familiar with terms like “sins,” “iniquities,” and “transgressions,” the phrase “dead works” adds to our understanding of what sin is and does. Sin is like touching a corpse. Sin is like coming into contact with death. And really, the word “like” doesn’t even need to be in the preceding two sentences. Sin is contact with death.
Contact with dead things had some serious consequences in the Old Testament that should not be written off just because we have the New. Touching the dead made one unclean, and being unclean meant one could not go to the tabernacle, the house of God. Or to put it another way: being unclean cut you off from the holy God until that holy God cleansed you.
We might relate this to the idea of “mortal sin,” an idea that Lutherans have clarified but have not discarded. The term “mortal” comes from the Latin MORS, ‘death.’ Since I have not spent a great deal of time studying the Lutheran use of the term “mortal sin,” I’ll simply quote from James 1:14-15, “But each person is tempted when he is lured and enticed by his own desire. Then desire when it has conceived gives birth to sin, and sin when it is fully grown brings forth death.”
Now we are cleansed, we have been brought into the land of the living. And therefore we love living things and we shun dead things. If we have been raised with Christ in Baptism and yet think we can be spiritual necrophiliacs, we will receive the inheritance of the dead.
If an Israelite loved touching dead things, it’s not that the cleansing rite would eventually cease to do anything. It’s that each time he touched the dead and went through the cleansing, there’s another week that he can’t go to the tabernacle. Now in the New Testament we have no rule saying that when we sin we have to let a week pass before coming to church. Yet we see that even without a rule the effects are somewhat the same. Those who love their dead works – not people who in the weakness of flesh succumb to temptation or are swindled by the devil, but who actually love their dead works – eventually cut themselves off from the Divine Service. They become like dead branches through whom the life-giving sap of Christ no longer flows. In the end, they are like the works they loved: dead.
Thinking of sins as “dead works” and understanding what that meant in the Old Testament, especially as we see in Numbers 19, should lead us to greater vigilance against “the one who has the power of death, that is, the devil” (Heb. 2:14). It certainly doesn’t help that our sinful flesh is naturally inclined toward the grave, but that’s cause for a fight, not for indulgence. As much as we still must call our bodies “this body of death” (Rom. 7:24), we also still cry out for rescue: “Who will deliver me from this body of death?” And as we see in Hebrews 9, so also Paul answers in Romans 7:25, “Thanks be to God through Jesus Christ our Lord!”