In the photo above, the moon gives the appearance of glowing as if it were producing its own light. However, the light that is seen is actually coming from the sun. Paul begins an explanation of the good news of the gospel by asserting that men can have righteousness from God through faith in Jesus Christ. This righteousness is not dependent on the law or on anything men can do in and of themselves. Just like moonlight does not come from the moon, this required righteousness does not come from men. Moonlight comes from the sun and the required righteousness comes from Jesus Christ.
Paul has just finished a lengthy portion of Scripture where he has pointed out that all men are ungodly and unrighteous and have absolutely no hope or desire to become righteous. They are under the wrath of God and do not have the ability to reconcile themselves to God. Man has, in fact, offended a holy and just God and cannot save himself from God’s wrath and just penalty. But now, as Paul says, God has intervened and provided what man cannot acquire on his own. He has provided the righteousness of God that is acquired through faith. Further, The Old Testament has pointed to this from the beginning of the Scriptures.
Praise God that He provides what he requires for reconciling sinful mankind to himself.