Romans 4:20-25
He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; And being fully persuaded that, what he had promised, he was able also to perform. And therefore it was imputed to him for righteousness. Now it was not written for his sake alone, that it was imputed to him; But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; Who was delivered for our offences, and was raised again for our justification.

Paul was explaining that faith, not works, is the avenue for righteousness and justification.  But faith in what?  What is it that we must believe?  Paul gives us the answer here first through the example of Abraham.  Abraham had believed in a promised son, from whom would come the nation of Israel.  Though he was old and his wife  barren, he’d believed God that that would happen.  After Isaac was born and God told him to sacrifice that beloved son, Abraham believed that Isaac would rise from the dead if necessary and that the promise of God would yet be fulfilled.

And it was fulfilled through Jesus Christ.  That is the Son about whom we must believe God—His own begotten Son who came into the world in a miraculous way and rose from the dead.  Because His death and resurrection is what brings our justification.  We must believe in the promise given, the promise fulfilled, and the promise still in effect that Jesus is enough.  Faith in Him is enough, because God is gracious enough to make it so.

What we believe affects a lot of things about our lives.  Our beliefs drive our actions and our attitudes.  Faith is the answer for sin and for our eternity, but it can’t be faith in just anything.  We must believe in God, in His Son who died for our sins and was raised from the dead.  We must believe in our gracious Savior who gives us true forgiveness and redemption, true freedom from sin.  And that faith is enough for us to be counted as righteous in the eyes of God.