A mentor of mine taught me the law of first mention in the Bible a few decades ago. If you are having trouble understanding a word or phrase in the Bible you can find where it was first mentioned in scripture and build on it from there. It is a valuable tool which helps you come to a biblical conclusion without having to read everyone else’s opinion. After all, does not the Spirit of truth guide us into all truth? (John 16:13)

The word blood was first mentioned in Genesis 4:10. It is the historical account of Cain and Abel:

8 And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.

9 And the LORD said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother’s keeper?

10 And he said, What hast thou done? the voice of thy brother’s blood crieth unto me from the ground. [Emphasis mine]

Now we know that man’s blood speaks to God. We can build on that.

Then we come to the blood of the lamb in exodus 12. It is the historical account of Passover:

 5 Your lamb shall be without blemish, a male of the first take it out from the sheep, or from the goats:

6 And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.

7 And they shall take of the blood and strike it on the two side posts and on the upper door post of the houses, wherein they shall eat it.

13 And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt. [Emphasis mine]

 Now we know that God sees the blood of the lamb.

13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:

14 How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?

Hebrews 9:13-14

Now we know the blood of sacrificial animals sanctifies to the purifying of the flesh but the blood of Christ purges your conscience from dead works to serve the living God.

24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.

Hebrews 12:24

Now, put it all together and we know that the blood of Jesus speaks more to God than any other shedding of blood.

When a person gets saved they are “turned from darkness to light, and from the power of Satan unto God”. The battle is now between the kingdom of darkness and the kingdom of light. You may have seen a news story, documentary, movie or an episode on a television show where some religious cult is making a blood sacrifice to gain spiritual strength (i.e., a chicken with its blood sprinkled around, or religious symbols written in blood). The kingdom of darkness knows that blood causes a rift in the spiritual realm. When we who are in the kingdom of light speak the name of Jesus his blood goes all the way to the throne of God.

How precious is the blood of Jesus?

28 Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood.

Acts 20:28

 It is the shed blood of Jesus that gives Christians power over the kingdom of darkness.