Leviticus 20:25
Ye shall therefore put difference between clean beasts and unclean, and between unclean fowls and clean: and ye shall not make your souls abominable by beast, or by fowl, or by any manner of living thing that creepeth on the ground, which I have separated from you as unclean.
The command is to put a difference between clean and unclean beasts and between clean and unclean fowls, and not to make the soul abominable by beast or by fowl or by any manner of living thing that creeps on the ground, which God has separated as unclean. It forbids defiling oneself by eating any creature God has set apart as unclean.
It belongs among the hygiene regulations given to Israel. It stands alongside the strict cleanliness required in the camp.
The dietary distinction was God's means of marking Israel as separated from other peoples. It belongs to the Lord's instruction to Israel to remain separate from the world. That separation included separation from the abominable practices of the Canaanites.
The food restrictions were not arbitrary. The prohibited creatures were unwholesome, and calling them unclean taught that eating harmful food defiles. What corrupts the body tends also to corrupt the soul. Such corruption leaves a person unfit for communion with God and for holy service.
The food regulations formed part of a discipline continued in the promised land. There each family's separate portion of land helped foster healthy habits and a natural way of life.