For God, who said, "Light shall shine out of darkness," is the One who has shone in our hearts to give the Light of the knowledge of the glory of God in the face of Christ. (2 Corinthians 4:6, NASB)
I've been making a big deal out of justification and how it is completely, utterly free. This is the wonderful truth of justification set forth in the Scriptures. And we've touched on eternal life a little. Not nearly enough, but a brief nod. We need to get back there eventually. But now let's look at things a little differently.
I believe 2 Corinthians 4:6 gives the most succinct definition of Christianity (not merely salvation, although it includes that) in the Bible. It stands out as possibly the most wonderful and most humbling verse. God commanded light to shine out of darkness, and it did: "Then God said, 'Let there be light'; and there was light." (Genesis 1:3, NASB). The same God has looked at sinful men and women, and commanded that light should shine out of their dark hearts: "the light of the knowledge of the glory of God in the face of Jesus Christ".
Let's consider this a minute. Who made this decision? The God who called light to shine out of darkness. Remember Romans 4:17 ? "God, who... calls into being that which does not exist" (NASB). Yeah, Him: the God who refused to leave well enough alone. The God who'd rather give His Son than to let sinners get what they deserve. The God who relentlessly pursues Hell-bound sinners, in order to drag them kicking and screaming into eternal life.
God demonstrated something in creation that has never been duplicated in the physical realm: God called something to come out of nothing. Morally, this is identical to what He has done in salvation: "When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross." (Colossians 2:13 & 14, NASB). He took nothing, and turned it into something.
This is a miracle, no less than creation was.
We frequently obscure the shining out of God's glory from our hearts. We still carry around this thing the Bible calls "the flesh", and sometimes it's hard to see past it. But it's shining there none the less. Remember Paul? A better man than any of us, he experienced this very thing in Romans 7. But God shone His glory out of the darkness of Paul's heart. The same God who didn't need anything to work with when He commanded light to shine from darkness, the same One who called light to shine out of Paul's heart; calls light to shine out of our hearts.
There is a school of thought out there that you need "fruit" to show for repentance: that you can't be sure you're forgiven unless your life has changed. I don't agree with that completely, but there is a sense where they're right. That is, God's work in a sinner's heart must inevitably result in something wonderful, new, and possibly a little scary. But there is a danger in looking at the saved man or woman with an obsession for finding "fruit": the danger lies in mis-crediting it. God called light to shine from darkness, He works out "fruit" in me without my help.
There's also a danger in rushing to judgement on something like "fruit". There are things God calls "fruit" that we consider repulsive: Abraham proved himself justified by his willingness to murder his son (James 2:21), Rahab proved her faith by committing treason (James 2:25). We're woefully bad judges of good fruit, and we need to bear that in mind. For an interesting read, go through Hebrews 11 some time, and compare what Hebrews says about the people there with what the Old Testament says about them. Consider Joseph: a wonderful young man, apparently without fault (although some think he was boastful about his dreams). What does Hebrews 11 commend him for? "By faith Joseph, when he was dying, made mention of the exodus of the sons of Israel, and gave orders concerning his bones" (Hebrews 11:22, NASB). Apparently of all the wonderful things Joseph did, this is what was worthy of record in the "faith chapter".
2 Corinthians 4:6 is a wonderful verse, because it describes God's work in our hearts in terms of how difficult it is: God is doing the impossible in His work in the hearts of sinners. But it's a humbling verse, because it shows just what we have to offer God: absolutely nothing.
But I wanted to bring up this wonderful, humbling verse; because it gives another perspective on salvation: the focus is on God's work in us. It reminds us that He didn't justify us just to desert us. Rather He's taken us in as His work: and He will certainly accomplish in us what He has set out to do (Philippians 1:6 ).
And what's the end that He has in store for us? "For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren" (Romans 8:29, NASB). There is a goal He has for us, a goal He is working towards right now. And to some degree, we who have been justified and have been given eternal life are all showing that now: He is bringing us into conformity wih His Son. He is making us all "little Christs".
He starts by uniting us with Christ in death and resurrection, but He continues by constant work in us: revealing the eternal life He has given us.
"Dear friends, now we are children of God, and what we will be has not yet been made known. But we know that when he appears, we shall be like him, for we shall see him as he is" (1 John 3:2, NASB). There is a day coming when we'll look at Him face to face: this is our goal, this is what motivates us. We'll see Him, and we'll be like Him. Not because God needs us, not because He has an ulterior motive in saving sinners. But because He wants us to share His delight in His Son.
And all the work He does for us and in us is to this end.