# You will become unclean until evening by these animals if you touch a carcass of one of them

"The dead bodies of these animals will make you unclean if you touch any of them"

# You will become unclean

A person who is unacceptable for God's purposes because he has touched one of these dead animals is spoken of as if the person were physically unclean.

# these animals

This refers to the animals he is about to list in the following verses.