Atonement merely covered lesser sins, but the sacrifice of Christ took away all sin.
"For it is not possible that the blood of bulls and of goats should take away sins" (Heb. 10:4).On the other hand, "the Lamb of God . . . taketh away the sin of the world" (John 1:29). The priest stood day by day offering sacrifices "which can never take away sins" (Heb. 10:11), but "by one offering he hath perfected for ever them that are sanctified" (Heb. 10:14).
Consider what the work of Christ did.
"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?" Hebrews 9:14
"[T]he blood of Jesus Christ his Son cleanseth us from all sin." 1 John 5:7
"[Jesus] loved us, and washed us from our sins in his own blood." Revelation 1:5
When Christ was finished with that action, "He sat down on the right hand of God" (Heb. 10:12). He could not have been seated unless His work was completed. His work was done because provision was made that not a vestige of sin would ultimately remain in man.
Atonement was for errors of ignorance, while the Lord's sacrifice was for all sin. In Leviticus, from the fourth chapter on we have the various directions for atonements for the sins of weakness and inadvertancy. The range of sins for which atonement could be offered was limited. The scope of Christ's work was far different. The Old Testament offerings would atone only for those of the nation Israel, not for anyone in the whole world.
Atonement was but a shadow of the coming substance of the work of the Lord Jesus Christ. Because atonement foreshadowed what would be revealed and achieved in the future, it could do nothing and was intended to do nothing for the future. Never was any atonement offered for sins not yet committed. Atonement looked only one way, back into the past, never forward into the future. The Redeemer, however, made "one sacrifice for sins for ever" (Heb. 10:12). As atonement was only for sins in the past, Christ's Work, if considered strictly as atonement, would be only for the sins which had been committed before the time the sacrifice was made. As an atonement, therefore, we could have no share in Christ's sacrifice, seeing that we have lived so far after it.
(Part Two to be continued)