What does "it" refer to in "Abraham believed God and it was counted to him for righteousness"?
In that statement, “it” modifies Abraham’s believing—his faith in what God had promised. Scripture counts Abraham’s act of believing, not any work or merit, as the basis for righteousness being imputed to him; God reckons His own righteousness to Abraham.
Les explains that in this verse the pronoun “it” modifies Abraham’s believing, his faith. It was his believing that was counted unto him for righteousness. God imputed to Abraham the very righteousness of God Himself, so that He could look at Abraham and say, in effect, “You’ve never sinned; you’re justified.” Abraham had done nothing—he simply believed. Then, as a result of his believing, he left town.