God had ordained from the very beginning that the wages of sin is death (Genesis 2:17). In his compassion, the Lord ordained that an animal could be slaughtered as a stand-in for the sinner so that in turn the sinner could be forgiven his sins. That animal in turn foreshadowed the slaughter of the Lamb of God (John 1:29). For his sacrifice to be acceptable to God, he had to be without sin himself. So any lamb that Old Testament Israel sacrificed had to be in perfect shape, without blemish or spot (Exodus 12:5; Leviticus 22:19–21; Deuteronomy 17:1).
19 but with the precious blood of Christ, like that of a lamb without blemish or spot.