Some Bible students use the law of first mention as a guideline of study in which they find the first time a word, idea, or doctrine is introduced in Scripture to better understand the other references. The idea is that the first time it is mentioned will be the simplest, most understandable reference from which the others build.
The law of first mention – What is it?
For example, blood is first mentioned when Cain kills Abel and God questions him about it: "And the LORD said, 'What have you done? The voice of your brother's blood is crying to me from the ground'" (Genesis 4:10). Here we see that blood relates to human life. We also see that the death of Abel, the spilling of his blood, is important to God. Later God tells Noah that He requires the blood (life) of murderers (Genesis 9:5–6). Then, we find that God instructs the Israelites to spread the blood of a lamb on their doors to avoid death in the first Passover (Exodus 12:1–13). This introduces the idea of substitution. An animal is given in exchange for a human life. This idea of substitutionary blood is extended through the covenant God makes with Israel in which He requires the spilled blood of perfect animals as a sacrifice in exchange for the forgiveness of individual and national sins (Leviticus 17:11).
Then, we see that Jesus sheds His blood for the forgiveness of all who call on Him (Isaiah 53:5; Mark 8:31–33; 10:45; John 1:29; 1 John 1:7; Revelation 5:6). Jesus fulfills the sacrificial system of the Mosaic Law and is our ultimate substitutionary atonement.
Hebrews 9:22 explains, "Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sin." Hebrews also explains that Jesus' sacrifice was made once and is finished. Unlike the sacrificial system of the Mosaic Law that was continually in effect for temporary atonement, Jesus' sacrifice provides complete and final atonement.
Studying the various mentions of blood in the Bible, beginning with the first, helps us more clearly see the significance of Jesus' shed blood.
Genesis contains many of the first mentions, of course. Jesus Himself refers to two, both about the creation of man and woman. In Matthew 19:4–5, referring to Genesis 1:27 and 2:24, Jesus said, "Have you not read that he who created them from the beginning made them male and female, and said, 'Therefore a man shall leave his father and his mother and hold fast to his wife and the two shall become one flesh?'"
As helpful as first mentions can be, care must be taken to keep all ideas, words, and doctrine of the Bible in context. For example, the first mention of a serpent is in the garden of Eden when Satan disguises himself as one. Later, though, the serpent on the pole is seen as a model of Christ (Numbers 21:9 and John 3:14).
Another challenge is determining when a first mention happens. Is it the first chronologically? Or is it the first mention in the books as they are ordered today? Or the first mention in the books as ordered in the Hebrew Bible?
First mentions can be helpful and useful in our study of the Bible. The law of first mention is not a rigid standard, but a helpful guideline when used along with other rules of solid hermeneutics.
"Do your best to present yourself to God as one approved, a worker who has no need to be ashamed, rightly handling the word of truth" (2 Timothy 2:15).
Is there a proper way to study the Bible?
What principles are used in biblical exegesis?
Why is context so important in studying the Bible? What is wrong with looking at verses out of context?
How can knowing Greek and Hebrew be helpful when studying the Bible?
Biblical hermeneutics – What is it?
Truth about the Bible