What does the Bible say about clean and unclean animals?

In Genesis 7, we see the distinction between clean and unclean animals even before the Levitical law was established. The raven, considered unclean, feeds off death and represents a nature that finds satisfaction in what is opposed to God's holiness. Conversely, the dove symbolizes purity and is used in sacrifices for those who could not afford a lamb. This dichotomy is significant for understanding the spiritual implications related to Christ, with the dove representing the Holy Spirit and the believer's nature that finds true rest only in Christ.