Adam and Eve discovered that blood must be applied to their lives to keep them from dying in their sins. They thought they could hide their sins from God by sewing fig leaves together to hide their naked bodies (Genesis 3:7).
Just like today, we cannot hide our sins from God and neither could Adam and Eve. Blood had to be shed and applied to their lives. So God sacrificed two animals and applied that blood by making coats of skin to clothe them (Genesis 3:21). God then kicked them out of the Garden of Eden to go forth and till the ground (Genesis 3:23).
Likewise, God used the blood of animals throughout the Old Testament to save the people from dying in their sins. Every year the High Priest, on the day of Atonement, sacrificed animals and sprinkled the blood on the Mercy Seat (Leviticus 16:14). They did this year after (Leviticus 16:34, Hebrews 10:1) to advance their forgiveness of sins. This was necessary because the blood of bulls and goats could not take away their sins (Hebrews 10:4).
God knew from the beginning that He would manifest Himself as Jesus Christ, so that His blood, the blood of a spotless lamb, would have to be shed (1 Peter 1:19-20) to give humanity the possibility of having their sins forgiven (Matthew 26:27-28).
The blood of Jesus Christ does not get applied to every human on earth automatically, otherwise we would have about eight billion people born again. It only gets applied to our lives when we obey the Gospel of Jesus Christ.
The Gospel of Jesus Christ is the death, burial and resurrection of Jesus Christ (1 Corinthians 15:1-4). And as Paul says in those verses, it is the obedience to the Gospel that saves us. Obviously then, when we obey the Gospel, the blood of Christ is applied to our lives. The question then is how do we obey the Gospel of Jesus Christ? In other words, how do we die, how are we buried and how are we resurrected. Jesus did this literally, and literally He was born again. But we only have to do this symbolically or figuratively, for us to be born again, and be able to get to heaven (John 3:3-5).
After Peter preached the Gospel to the crowd gathered on the day of Pentecost in Acts 2, they asked Peter and the elven apostles with him, " Men and brethren, what shall we do?" (Acts 2:37). Peter then gave them this command:
Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost (Acts 2:38).
That day the blood of Christ was applied to about 3000 souls (Acts 2:41). They were baptized in the name of Jesus Christ for the remission of their sins and filled with the Holy Ghost, with the evidence of speaking in tongues.
Let us make sure we have the blood of Jesus Christ applied to our lives by obeying the Gospel by obeying Acts 2:38, in the name of Jesus Christ.