Your question, How does Christ’s blood "cleanse from our sins? 1 Peter 1:18 “Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; But with the precious blood of Christ, as of a lamb without blemish and without spot: Now if you stop short of reading this verse you would not have seen the rest. “Who verily was foreordained before the foundation of the world, but was manifest in these last times for you, Who by him do believe in God, that raised him up from the dead, and gave him glory; that your faith and hope might be in God. Peter is telling us that Jesus was foreordained before the foundation of the world. Jesus was determined to be God’s sacrifice for sin. To redeem us from our sin. This included his crucifixion. As the Apostle wrote without the shedding of blood there is no remission of sins. God revealed this fact to Israel through signs. They would annually sacrifice the blood of animals to cover their sins. This demonstrated that the blood of animals would cover their sins, pointing to Jesus. These examples served as a reminder to Israel that a sacrifice was necessary to cleanse their sins. Hebrews 9:22 “And almost all things are by the law purged with blood; and without shedding of blood is no remission. Now we know that God made Jesus his sacrifice before the foundation of the world that through his shedding of blood would cleanse us from all our sins.