Did Abraham first have faith in Genesis 15:6, or when he left Ur, as in Hebrews 11:8? Also, did Abraham know he was justified?

This text is from a letter written by David Gooding in 1999.

In answer to your first question, I think it is helpful to notice how the principles of salvation are taught and exemplified in the Old Testament.

For instance, the principle of redemption by the blood of the lamb is illustrated in Exodus 12 by how Israel's firstborns were saved from the judgment of God. On the other hand, the principle that we are born again by faith in Christ, who was for our sakes lifted up upon a cross, is illustrated in the history of Israel, not when they came out of Egypt but after they had been many years in the wilderness (see Numbers 21:4–9).

Now, when we survey Old Testament illustrations of these basic principles, we are not meant to deduce from them that redemption by the blood of Christ occurs when we first repent of our sins and trust the Saviour; and that being born again is something that happens only afterwards, on the road towards our inheritance. Rather, both justification by faith and the new birth happen simultaneously at the moment when we trust the Saviour.

To go back to Abraham and his justification: When Genesis 15:6 announces that Abraham was justified by faith when he believed God, it is held up for our consideration because it explicitly and accurately expresses the basic condition for justification, which is simply faith in God. Romans 4 discusses with us in detail the analogy between Abraham's faith on that occasion and our faith. When Abraham believed God and it was counted to him for righteousness, the matter over which he believed God was the announcement that he would have a son.

Now, when we believe God and are justified by faith, we are not asked to believe that God is going to give us a child in the sense that Abraham was given a child. The principle in common between us and Abraham is that Abraham was required to believe solely in God who could bring new physical life out of bodies—i.e. Abraham's and Sarah's—which were physically as good as dead. For us, being justified by faith means putting our faith for salvation and eternal life solely and only in God, who raised our Lord Jesus from the dead.

In Abraham's story, Genesis 15:6 does not stand by itself. It is the beginning of a long story. Abraham certainly believed God. It was genuine faith; but in Genesis 15, 16 and 17 his faith, though genuine, was not totally consistent. He and Sarah believed that God was going to give them a child, but they imagined that faith in God meant doing the best they could by their own efforts to fulfil that promise of God. God then had to teach them that this was not so. When God promised Abraham a son, he meant it as a promise and not as an exhortation to Abraham and Sarah to do their human best. And so, Abraham's faith had to be refined.

It was, as I say, genuine to start with; but it had to be refined until Sarah and Abraham came to the point where both their bodies were beyond being able to produce a child, both being as good as dead, and they had to depend utterly, wholly and solely upon God to fulfil the promise that he had made to them—the promise that they had originally believed.

Romans 4 applies this lesson—not just Genesis 15, but the whole story from Genesis 15 to Genesis 21. Similarly, Galatians 3 and 4 preach to us not just Genesis 15:6 but the whole trajectory from Genesis 15 to Genesis 21.

It seems to me, therefore, that God in his wisdom allowed Abraham to go through this long chain of experience in order to illustrate for us precisely what is meant by faith when that word is used in the phrase 'justification by faith'. This is important because there are many people still who, like the Galatians to whom Paul wrote his letter, begin by genuinely believing in God for justification, but thereafter become somewhat confused in their minds as to what faith really means, and sometimes allow themselves to be persuaded that for salvation they need to add to their faith various rituals or merits. For these people, Abraham's experience throughout chapters 15–21 of Genesis becomes an exceedingly important example.

As to your second question, whether Abraham knew he was justified, my simple answer would be yes, certainly he knew! Genesis 15 itself shows that, because the promise God made to Abraham on that occasion would be that he would have a son, and that son would inherit all that God gave to Abraham, Abraham believed God, and it was counted to him for righteousness. But then Abraham asked God how he could be truly sure of the inheritance that God was promising, and God's answer was that he made a covenant with Abraham to guarantee to him there and then that the promise Abraham had just believed would be completely fulfilled. Abraham, therefore, knew that he had been accepted by God.