The word "separate" could be better translated as consecrate, meaning they dedicate themselves.
John W. Ritenbaugh
New Covenant Priesthood (Part 2)
I Peter 1:16 says, ". . . because it is written, 'Be holy, for I am holy,'" which is precisely the lesson contained within Leviticus 22:1-7. Our holy God is clearly saying, "Those who serve Me must also be holy." Holy essentially means "set apart," but it also carries with it the sense of "different," which helps explain why a person or thing is set apart. Certain factors or characteristics distinguish the set-apart one or thing, making it different from persons or things of the same kind.
Holy also has the sense of cleanliness or of being undefiled. God can just as easily be saying to the priests and their children, "I am a clean God, and I want those who serve Me to be clean." In this case, His transcendent purity of intent and character sets Him apart from others or things that people may consider to be god. He is therefore completely undefiled.
The Leviticus passage mentions leprosy, a corpse, and semen. We must not forget that, when this was written, God was addressing a carnal people. Thus, the instruction is couched in physical terms, but we must look for spiritual meaning within the physical instruction.
The Tabernacle, altar, priesthood, furniture, vessels, and all of the rites have spiritual significance, and Paul writes that they are "shadow[s] of good things to come" (Hebrews 10:1). Leprosy is a horrible, dreadful disease, thus it is a type of a spiritual disease. It is externally visible in its disfigurement of its victim's body. At times, there can be running sores. It probably does not parallel any one spiritual disease, but rather it symbolizes any number of sins that disfigure a person's character and/or attitude.
Both a corpse and semen possibly represent carriers of disease. Something causes a person to die, and all too frequently, it is an invisible, internal disease, of which infections and cancers are examples. The widespread AIDS virus is a good example. It can be carried within a man's semen into a woman's body. The carrier may look healthy externally, but a deadly disease is present. Only the carrier may know of its existence within him. A corpse and semen represent sins that are not easily perceived. Withdrawal from participation in the fellowship requires the sinner to exercise discipline, as he may be the only one aware of his problem. Creeping things are also defilements from sins that are less obvious. Perhaps in this case, it might be problems with one's attitudes like resentment, bitterness, envy, jealousy, and lusting.
Regardless of what rendered a person unclean, he was not allowed to participate until he cleaned himself by washing in water, a type of the Holy Spirit. Even then, he was still considered unclean until evening of that same day. This process was a form of excommunication. The unclean person was symbolically excluded from communion with God and held unfit to eat of the holy food of the altar, symbolizing the Word of God, until he had cleaned up his act. Verse 7 distinctly says he was free to eat of the holy things only after the sun went down. Even given this permission, he was still eating in the dark! Though accepted back into fellowship, he was still somewhat removed from full exposure to the light of God's throne until the next day, when complete communication with God was restored.
Taking steps to rid ourselves of uncleanness has awesome ramifications when we grasp how burdened we are with the potential for sin. The apostle Paul labels himself as a wretched man who greatly needed deliverance (Romans 7:24-25). Despite what we can do on our own—and God requires us to strive to do so—complete deliverance can only come through the work of Jesus Christ. It is essential that we know this, yet it is perhaps beyond our full understanding and appreciation that God is so merciful and full of grace to provide the sin offering that precedes us! If it were not for these elements—because we are so full of spiritual creeping things and spiritual leprosy—we would never be permitted to eat from the Lord's table.
I and II Corinthians offers us great comfort by showing that, though one may be cut off from the body, he can return once he has cleaned himself through repentance. It shows that even though he is denied close communion with God because of some spiritual uncleanness, he still remains tied to God through the New Testament priesthood. Disfellowshipping is intended to be a temporary, corrective tool.
I Corinthians 5:4-5 says, "In the name of our Lord Jesus Christ, when you are gathered together, along with my spirit, with the power of our Lord Jesus Christ, deliver such a one to Satan for the destruction of the flesh, that his spirit may be saved in the day of the Lord Jesus." The purpose of excommunication is to save the person from his uncleanness that is destroying his communion with God and others in the fellowship. Therefore, if he can still be saved, that person is not completely cut off from God.
II Corinthians 6:14-17 adds more information to this subject. Paul asks four questions that provide comparisons that clearly urge us to avoid or depart from what is unclean so that we can be at peace and in communion with God. Fellowship with God and being allowed to eat spiritual food from His table are clearly conditioned upon our not falling into uncleanness but instead striving to maintain the purity provided by Christ's sacrifice.
Our part in striving to maintain the purity is to follow Christ's example of thorough dedication in fulfilling the requirements of the burnt and meal offerings. Doing so in no way earns us the fellowshipping privileges expressed in the peace offering, but it does show God our understanding of faith, love, sacrifice, thanksgiving, and the links between total devotion to Him, Jesus Christ, our fellow man, and His wonderful purpose. God has invested a great deal to provide this for us. The least we can do is give back to Him full devotion in our life as a living sacrifice.
John W. Ritenbaugh
The Offerings of Leviticus (Part Five): The Peace Offering, Sacrifice, and Love