In the Old Covenant, the priest offered sacrifices and sprinklings of blood which merely effected an external pardon. This absolution rendered no one inwardly holy and just before God. Something beyond this was necessary to secure true forgiveness. According to Martin Luther:
But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building; Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us. For if the blood of bulls and of goats, and the ashes of a heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God? And for this cause he is the mediator of the new testament that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance. (Hebrews 9:11-15, Luther’s Translation?)
An understanding of practically all of the Epistle to the Hebrews is necessary before we can hope to make this text clear to ourselves. Briefly, the epistle treats of a twofold priesthood. The former priesthood was a material one, with material adornment, tabernacle, sacrifices and with pardon couched in ritual; material were all its appointments. The new order is a spiritual priesthood, with spiritual adornments, spiritual tabernacle and sacrifices–spiritual in all that pertains to it. Christ, in the exercise of his priestly office, in the sacrifice on the cross, was not adorned with silk and gold and precious stones, but with divine love, wisdom, patience, obedience and all virtues. His adornment was apparent to none but God and possessors, of the Spirit, for it was spiritual.
Christ sacrificed not goats nor calves nor birds; not bread; not blood nor flesh, as did Aaron and his posterity: he offered his own body and blood, and the manner of the sacrifice was spiritual; for it took place through the Holy Spirit, as here stated. Though the body and blood of Christ were visible the same as any other material object, the fact that he offered them as a sacrifice was not apparent. It was not a visible sacrifice, as in the case of offerings at the hands of Aaron. Then the goat or calf, the flesh and blood, were material sacrifices visibly offered, and recognized as sacrifices. But Christ offered himself in the heart before God. His sacrifice was perceptible to no mortal. Therefore, his bodily flesh and blood becomes a spiritual sacrifice. Similarly, we Christians, the posterity of Christ our Aaron, offer up our own bodies (Rom 12:1). And our offering is likewise a spiritual sacrifice, or, as Paul has it, a “reasonable service”; for we make it in spirit, and it is beheld of God alone.
Again, in the new order, the tabernacle or house is spiritual; for it is heaven, or the presence of God. Christ hung upon a cross; he was not offered in a temple. He was offered before the eyes of God, and there he still abides. The cross is an altar in a spiritual sense. The material cross was indeed visible, but none knew it as Christ’s altar. Again, his prayer, his sprinkled blood, his burnt incense, were all spiritual, for it was all wrought through his spirit. Accordingly, the fruit and blessing of his office and sacrifice, the forgiveness of our sins and our justification, are likewise spiritual. (“Christ Our Great High Priest”)