Throughout the Old Testament, a spotless animal was permitted to die in place of the sinner. Sin required death—either the death of the sinner or the death of an allowed substitute. No person in the Old Testament was qualified to be a sin sacrifice, as Jesus was, so animals were used as pictures to teach about the future Christ. These animals were, in various ways, pictured as being made one with the sinners in order to point to Christ being made one with believers. The first sacrifice was when God made clothing of animal skin to cover the nakedness of Adam and Eve, whose sin incurred their nakedness and need of clothing. This was such a beautiful picture of substitutionary sacrifice! Imagine them wearing the skin of this animal, which gave its life to pay for their sin. What a picture of union between sinner and sacrifice. The skin from the animal’s back was now on their back—they were walking around in its skin as if they had become the animal; while it had died for their sin as if it had become them.
Adam was the firstborn of humanity—the first Adam. Christ was the Last Adam. There are only two races, the race of the firstborn and that of the Lastborn—of Adam and of Christ. This also is pictured throughout the Old Testament. Cain, the firstborn killed Able and lost the birthright. Seth gained it and Christ would come through his line. Esau sold his birthright for sinful greed, and the lastborn, Jacob, gained it. And how did he gain it? By putting on the skin of the firstborn, so to speak—the skin of an animal as substitute for the skin of Esau—and going to the father in place of the firstborn. That which Esau had coming was then given to Jacob in his place. What did Isaac say? “The voice is Jacob’s voice, but the hands are the hands of Esau.” And when the time was right, God the Son put on the same hairy skin that we have—our humanity and our flesh and bones—and went before the Father in our place to take what we had coming. Can you imagine God saying, “The voice is God’s voice, but the hands are the hands of a man,” as the Lastborn Savior died in place of all of the firstborn who would believe in Him?
The last plague to free the Hebrews from Egypt was the death of the firstborn. But those households of faith had their firstborn saved by the sacrifice of a lamb. After killing the lamb, they had to put its blood on the wooden doorpost. Perhaps it would have been a clearer picture for us if they had to nail the lamb to the doorpost. But the blood should be sufficient. After that, they had to eat the lamb in its entirety (or burn what they could not finish). This, too, was a picture of the oneness of Christ and the believer that would one day come. The sinner must be made one with the sacrifice. By eating it, they were bringing it into their being and becoming one with it.
Jump forward to the New Testament and we find that we are to remember Christ’s death in our place by eating the bread which is His body broken for us and drinking the wine which is His blood shed for us. This symbolized becoming one with His sacrificial death by becoming one with Him. Rom. 6:3, “Do you not know that as many as are [immersed] into Christ are [immersed] into His death?” This is not immersion into water but into His Spirit, by His Spirit being put into us as He sends the Spirit of His Son into our hearts crying, “Abba! Father!” By thus being united to Christ’s spirit, we are united to His death—as well as united to His life, both His current life in us now and His past life on earth. We are joined in human identity to Jesus and we gain an ownership in His righteous deeds and His atoning death just as if we had done it instead of Him! We are saved from our sins by the blood of the Lamb of God, because that Lamb is in us and we are one with Him!