The concept of Christ's blood confuses some people, but without a proper understanding of it, believers cannot appropriate its power.
When Adam sinned, his sin was passed down through his blood. David acknowledged this truth in Psalm 51:5: Behold, I was brought forth in [a state of] iniquity; my mother was sinful who conceived me [and I too am sinful].
Jesus came to redeem mankind, to purchase our freedom and to restore us to our original state. How could He possibly do that with sinful blood?
Jesus is referred to as the “last Adam” in 1 Corinthians 15:45. Because He was born of God, not man, there is life in the blood of Jesus, and when it is properly applied, the life in His blood will conquer and overcome the death that works in us through sin.
God wants to restore us to the place of authority that is ours. He has already made all the arrangements. We might say that He has "sealed the deal." The purchase price has been paid in full. We have been purchased with a price—the precious blood of Jesus.