Genesis 15:6 is the key verse in all of Genesis, maybe in all of the Old Testament. It is quoted four times in the New Testament (Romans 4:3, Romans 4:22, Galatians 3:6, and James 2:23). Read the whole chapter for context (only 21 verses).
A commonly-asked question goes like this: “So what about the people who lived in Old Testament times, before Jesus came? Are they just without hope for salvation?” The answer is no, and Genesis 15:6 explains why. I’ve previously explored how much of his nature and character the Lord has revealed about Himself in the first 11 chapters of Genesis, before Abram was even born. From the first 11 chapters of Genesis, we know that there is a God who created us, we have rebelled against Him, and that he will redeem those He has chosen to redeem as they trust in Him. That is the gospel. Yes, of course, the specifics get fleshed-out over the rest of Scripture, as God progressively reveals more and more about Himself to us. We will learn in the pages to come just how hard our hearts really are, and that only God is able to breath life into the dead and depraved human heart. We will learn that there is only one God and that He has a name. We will learn more about His character. We will learn specific ways in which our sin separates us from God and keeps us from seeing His glory. And, in the New Testament, God will ultimately reveal Himself through His Son and through His church. Abram didn’t have all that information, but he did know that His only hope of receiving God’s promise was to trust in God’s Word, as it had been revealed to him at that point.
And he believed the LORD, and he counted it to him as righteousness. (Genesis 15:6)
You could say that this verse is where Abram gets “saved.” This verse is how we know that Abram is in heaven with the Lord right now. Throughout Scripture, righteousness is God’s standard for what it takes to receive His favor. This verse is saying that God is going to “count” Abram’s faith in God’s promise of redemption through his lineage “as righteousness.” Let me say it a different way. God is going to “count as righteousness” Abram’s faith in His promise, even though Abram has not achieved righteousness (in fact, he is going to fall again in the very next chapter). The theological term for this “counting as righteousness” is called “justification.” So, in the New Testament, you will see that we are “justified by faith.” A simple way to define “justification” is that it is the way that God makes it “just as if” we had never sinned. Pure, holy, righteous. Just as if Genesis 3 had never happened. Just as if we had never sinned. That is how God sees those he has justified by faith. It seems completely not fair. You can be the worst sinner ever (which in actuality we all are, God doesn’t have categories of sins because he hates all sin), and you can be “just as if you’d never sinned” to God. How is that fair? Just ask Jesus. He never sinned, yet he took upon himself the sins of every man, woman and child who ever existed. He died in our place. He died in Abram’s place. He died in place of every person who would trust Him. That wasn’t fair either. Yet it was that unfairness toward Christ that makes God’s justification fair towards us. Because of what Christ did on the cross, God’s righteous wrath towards us has been completely satisfied.
For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God. (2 Corinthians 5:21)
This is exactly the way that people come to God today. In fact, that is precisely the point of those four verses that are listed above from the New Testament in which Genesis 15:6 is quoted. We are saved today the same way Abram was saved 4,000 years ago – through faith in what God has promised us in His Word. We have a lot more of God’s Word than Abram had, and we also have His living Word (Jesus – John 1:1-14). Just as Abram trusted in what God had revealed to him (just a glimmer of God’s future redemptive plan), we are to trust in that which God has revealed to us (His redemption through His Son Jesus). Scripture makes it clear that, even in Abram’s time, people had enough revealed knowledge of God that they were without excuse, because He has revealed Himself in all of creation. (Romans 1:20) That being the case, we are well beyond excuse.