What does Genesis 15:6 mean?

For Christians, this is one of the key verses in all the Old Testament. Abram responded to God's latest promises with doubts, asking how God's promises could be true if he still did not have a son. And yet, Abram also willingly received the reassurance of God's Word. After God showed him the stars and promised once more that Abram's descendants would be uncountable, Abram chose to continue to believe God.

It's important to note here that this is not the beginning of Abram's faith. It is a statement about his continuing belief in God. This is more than assumption: the Hebrew word used in this verse, from the root word 'aman is in a form which implies something that occurred before this encounter. This moment of trust, during the vision of chapter 15, is not the instant where Abram "finally" came to faith in God. He has expressed faith in God—and that faith is the reason he is choosing to trust God now.

More importantly, this is a statement about how any sinful human could possibly be counted as righteous in any way by a perfectly holy God. Abram's heroic rescue of Lot, from chapter 14, was not credited to him as righteousness. His believing the Lord was what was counted as righteousness. It is faith in God that makes people acceptable to God. This idea is key to Christianity, and this verse is referenced by the New Testament writers in Romans 4:3, Galatians 3:6, and James 2:23.

God kept His word. Abram will be renamed Abraham, and his descendants will become Israel, the uncountable people of God. However, as Paul will write in Galatians 3:6, millennia after Abram, all those who trust God are the sons of Father Abraham, who believed.