Why was Jesus' blood divine and not sinful?
Christ's blood was divine and not sinful because the seed of the woman was kept insulated from the curse, carrying no sin nature down to Mary. Since the fetal blood system comes from the father, and Christ had no earthly father, His blood originated with God, while His humanity came from Mary's ovum.
Les explains that Scripture emphasizes the seed of the woman to prove Christ was the rightful heir to David's throne through Mary's bloodline. The seed of the woman was spoken of in Genesis 3 and was kept insulated from the curse, so no sin nature passed down to Mary. Therefore Mary could conceive of God and bear a child whose blood was divine, not sinful, without an Adamic nature, because there was no earthly father. Les also points out that the blood system of every fetus comes from the man, not the mother, so the virgin birth fits physiologically and scientifically: Christ's blood system originated with God as Father, yet He was human because He was born of the ovum, egg, or seed of the woman. The genealogies also show Joseph as legal father and Mary as physical mother, both lines going back to David and then Abraham.
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.