“What saith the Scripture? Abraham believed God, and it was counted to him for righteousness” (Rom.4:3).
The Apostle Paul uses the above quotation from Genesis 15:6 to prove that “to him that worketh not, but believeth on Him that justifieth the ungodly, his faith is counted for righteousness” (Rom. 4:5).
It is wonderful that God does not require — indeed, does not permit — human works for salvation, but only faith. But the question is: What is faith? What kind of believing saves?
There is no indication in Scripture that “the gospel of the grace of God” or “the preaching of the cross” was proclaimed to Abraham. We must go back to the passage which Paul quotes to see what Abraham believed. Genesis 15:5 says:
“And [God] took [Abraham] forth abroad, and said, Look now toward heaven, and tell [count] the stars, if thou be able to number [count] them: and He said unto him, So shall thy seed be.”
It is this simple, wonderful promise about the multiplication of Abraham’s seed which is followed with the words: “And he believed in the Lord; and He counted [reckoned] it to him for righteousness” (Genesis 15:6). We do not mean to imply that this was the first expression of Abraham’s faith, for in Hebrews 11:8 we read:
“By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither he went.”
This took place considerably before the Genesis 15 incident and we are specifically told that through his faith he “obtained a good report” (Heb. 11:2).
From all this it is clear that Abraham believed what God told him and was counted righteous — as we now know, through a redemption still to be wrought by Christ. We, now, must believe what God tells us — and this is nothing less than the account of the all-sufficient finished work of Christ, wrought in our behalf, on Calvary’s cross.
“[He] was delivered for our offences, and was raised again for our justification” (Rom. 4:25). source