Leviticus 11:46-47 (ESV)
This is the law about beast and bird and every living creature that moves through the waters and every creature that swarms on the ground, to make a distinction between the unclean and the clean and between the living creature that may be eaten and the living creature that may not be eaten.
Because God is holy He wants His children to be holy. He wants them to be separate and clean. These warnings in Leviticus about eating some types of animals and fish and reptiles and not eating others served to keep the nation clean. They were to be clean in three ways:
1. Health. Because there was no refrigeration, or anything to keep food from becoming spoiled or contaminated, they had to be careful what they ate. They were always on the move and an outbreak of heath issues in the camp would be a hinderance to their nation.
2. Separate from the world. They were to be separate from the nations around them. They were to make sure they did not take up the habits of eating that the foreign nations did. This is the reason Daniel did not eat the kings food (Daniel 1).
3. Example. Since God is holy and has no unclean thing in His character, they, too, were to be holy. They were to act different and strive for holiness. Being obedient to God was an act of holiness. Since God told them not to eat these things it would be unholy to do so because that would be an act of disobedience.
God wants us holy today. We don’t have the same health issues (or, do we?). But we are to separate from the world and to act different. That can and should include our eating habits.
1 Peter 1:13-16 (ESV)
Called to Be Holy
Therefore, preparing your minds for action, and being sober-minded, set your hope fully on the grace that will be brought to you at the revelation of Jesus Christ. As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct, since it is written, “You shall be holy, for I am holy.”