Why must the unclean be redeemed according to the Bible?

In Exodus 13, there is a clear distinction made concerning the unclean and clean, particularly in reference to the firstborn. The principle laid out is that the unclean must either be redeemed or sacrificed, pointing to the ultimate necessity for redemption through Christ. This foreshadows the gospel message that all humanity is unclean by nature and, without redemption, faces spiritual death. The sacrificial system set in place was a picture of Jesus Christ, who would be the ultimate sacrifice for all who believed in Him. This theme is crucial to understanding God's plan for salvation which demands both justice for sin and the offering of grace to the unworthy.