Paul stated a timeless truth when he wrote:
"Therefore by the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin." —Rom 3:20

Even under the law in the OT, the works of the law could have nothing to do with a man's eternal salvation. Salvation finds its true basis in Christ's sacrifice on the Cross and has always been by grace through faith. To deny this is to oppose the whole doctrine of justification presented in Romans.

One of the best examples of God's grace in the OT is found in the story of Saul. Saul's regeneration is recorded in 1 Sam 10:1-10.

To be sure, Saul's life as a whole was anything but victorious. As the end nears for Saul, he consults a spiritist medium (1 Samuel 28) and then dies by his own hand (1 Sam 31:4-6).

These final acts in Saul's life certainly do not indicate that he was unsaved. On the contrary, they constitute a warning to all the saved about the dangers that come from not walking with God by faith. Saul is a classic example of a regenerate man who never learned to live by faith.

The author of Samuel makes it quite clear that Saul was born again. Although he does not use these exact words, his language is perfectly plain.

After Samuel anointed Saul to be king over Israel (1 Sam 10:1), he tells Saul about the various signs that will happen to him after he leaves Samuel's presence (10:2-4). Finally, Samuel says:

"After that [an encounter with three men] you will come to the hill of God where the Philistine garrison is. And it will happen, when you have come there to the city, that you will meet a group of prophets coming down from the high place with a stringed instrument, a tambourine, a flute, and a harp before them; and they will be prophesying. Then the Spirit of the Lord will come upon you, and you will prophesy with them and be turned into another man." —1 Sam 10:5-6 (emphasis added)

The events Samuel had predicted all came to pass, as is indicated in vv 9-13. Verse 9 gives us a summary statement as follows:

"So it was, when he turned his back to go from Samuel, that God gave him another heart; and all these signs came to pass that day." —1 Sam 10:9 (emphasis added)

Note that v 9 gives precedence to Saul's transformation due to its importance. But v 6 makes it clear that this event did not occur first, but during his encounter with the group of prophets.

It would be pointless to quibble over the meaning of the statements I have italicized in vv 6 and 9. Surely they can refer to nothing other than new birth. How else can a sinner be turned into another man or be given another heart than by regeneration? Clearly Saul was saved on this day!

But it should also be noted that this occurs during an encounter with a group of prophets who are in the process of prophesying. Of what then were they prophesying? There is no good reason to doubt that they were prophesying about Israel's Messianic hope.

The Apostle Peter told us:

"To Him give all the prophets witness that, through His name, whoever believes in Him will receive remission of sins." —Acts 10:43

Of course, Peter was speaking of the prophets who had written books of Scripture. But who can doubt that the prophets in OT times often spoke orally of these things?

In fact, the Messianic hope was clearly crystallized even as early as the time of Moses. Thus the writer of Hebrews can say of Moses:

"By faith Moses, when he became of age, refused to be called the son of Pharaoh's daughter, choosing rather to suffer affliction with the people of God than to enjoy the passing pleasure of sin, esteeming the reproach of Christ [Greek = the Christ, i.e., the Messiah] greater riches than the treasures of Egypt; for he looked to the reward."  —Heb 11:24-26

So Moses not only believed in the Messiah, but also pursued eternal reward—just as we should.

Let it be said, then, that Saul—like ourselves—was saved by faith in the Messiah. No other conclusion is reasonable. When Saul joined in with the prophesying of the prophets, he did so as a result of believing what they were saying. The Holy Spirit's regenerating work is evidenced by Saul joining the prophetic testimony.

But even if he had not prophesied, he was still a new man with a new heart. The prophesying simply made manifest to the nation that, like Samuel himself (1 Samuel 3), Saul had come to know the God of Israel.