God established as law that almost everything should be purified with blood.
And according to the law almost all things are purified with blood, and without shedding of blood there is no remission. (Hebrews 9:22, NKJV)
Under the old covenant, the Jews offered sacrifices of animals to be purified of their sins. God gave his only begotten son as a perfect sacrifice. The son of God's blood was shed for us. The blood of animals cleanses only the flesh, the blood of Jesus cleanses our conscience from dead works.
Not with the blood of goats and calves, but with His own blood He entered the Most Holy Place once for all, having obtained eternal redemption. For if the blood of bulls and goats and the ashes of a heifer, sprinkling the unclean, sanctifies for the purifying of the flesh, how much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, cleanse your conscience from dead works to serve the living God? (Hebrews 9:12-14, NKJV).
Jesus is the perfect sacrifice to save men and he was raised from the dead on the third day, that is why he can save men perfectly as he is alive.
Therefore He is also able to save to the uttermost those who come to God through Him, since He always lives to make intercession for them. (Hebrews 7:25, NKJV).