Therefore, whether you eat or drink, or whatever you do, do all to the glory of God. 1 Corinthians 10:31
The Lord has set his people free from bondage and now has begun establishing them as a holy nation unto Himself by defining how they are to be set apart for His purpose.
This is holiness.
God has given Moses the blueprints for the tabernacle as a place for man to meet Him and He has given specific instructions how they are to worship Him in their offerings of thanks and atonement.
Now come the rules of cleanliness. The closer you get to God, the cleaner you have to be.
1. God defines "clean" to establish a holy nation for Himself.
In Leviticus 11, the Lord speaks to Moses and Aaron and defines what may and may not be eaten.
Cows fine. Camels nope. Fish no problem. Alligators forget about it. Chickens sure. Vultures no way. Grasshoppers have at it. Spiders definitely not.
He spells it out for them, even so much as being anatomic because we are like sheep not too bright; and it's in the absoluteness of His instructions that we begin to realize how much God wants us to be "unlike" the those that won't believe and, more importantly, holy like Him.
2. God defines "clean" to nurture a disciplined faith for that nation.
In the Old Testament, the act of cleanliness took on a physical nature, even so much as to being ceremonial so the people would treat it with the highest regard in maintaining a closeness with God.
How does one become clean? By understanding what it is to be unclean.
Touching the carcass of an abominable animal would constitute a person being sent outside the camp until evening. A woman, during her "flow," was sent outside the camp for a period of time, as was a man who laid with his wife during said time.
The idea was simple in the center of the camp was the tabernacle and in the middle of the tabernacle was God, who was by their understanding, in the Holiest of Holies. The clean were in the camp close to Him, while the unclean were sent outside the camp or further from Him.
This discipline was necessary for man to realize how holy He is and to grow through instruction to be a holy people.
3. Jesus redefines "clean" to establish a royal priesthood of all believers.
The New Testament sheds a "new" light on the cleanliness thing because now God is amongst the people. Years have passed and the unclean are regarded as the bottom of the food chain, but atonement has taken on the nature of man and Jesus explains clean and unclean in spiritual terms; sin is unclean and righteousness clean.
The designs of the Father are explained by the arrival of the Son as He healed physical maladies of "not-so-clean" proportions, such as leprosy, crippling diseases and blindness to explain righteousness through faith in Him.
The leper says to Jesus, If you are willing, You can make me clean. To which Jesus replies, I am willing, be cleansed. How cool is that?!!
By believing in the Lord and in His healing power, we are restored to "cleanness" and brought closer to Him. We no longer have to live outside the camp in shame because our faith in Jesus Christ, not only washes us but, places us with the Father in the Holiest of Holies.