Acts 20:24 But none of these things move me, neither count I my life dear unto myself, so that I might finish my course with joy, and the ministry, which I have received of the Lord Jesus, to testify the gospel of the grace of God.
There you have it. The extent of the grace of God was not revealed until it was given to Paul. Throughout the Old Testament and through the death of Christ action was needed. There were sacrifices, feast days, circumcision and many other rules and conditions. Not until after Christ ascended to heaven and the Holy Spirit had been given was there any understanding of the free gift of salvation through no merit on man’s part. That was the revelation that was given to Paul. The other apostles didn't get that revelation untill Paul told them. That's why Peter said it was "hard to understand". The Jews didn’t understand the change that occurred at Christ’s death and resurrection and many Christians today don’t understand the change that occurred when the Holy Spirit was given. That was the revelation that was given to Paul.
What is the term "gospel"? GOOD NEWS. God has been giving good news since the fall of Adam. THAT is what the Bible is all about: God's GOOD NEWS to man.
So, what is "the mystery of the gospel;" WHAT was SECRET of the good news? How could a holy and righteous God proclaim good news to sinners? How could He JUSTLY offer them good things to come when, as sinners, they DESERVED His wrath? The answer is found in the epistles of PAUL.
If anything is made clear in the Pauline epistles it is the act that the secret of all GOd's good news to man is centered in CALVARY. It was because Christ was to die for sin that God could proclaim good news to sinners, whether it concerned the bringing in of the millennial kingdom, the blessing of the nations THROUGH Abraham's seed (Israel) or the final defeat of Satan.
It was not until some time after the crucifixion, however, that the SECRET of the gospel was revealed TO AND THROUGH THE APOSTLE PAUL, and with IT the best news of all: "THE GOSPEL OF THE GRACE OF GOD."
The proclamation of "the gospel of the grace of God" was the natural accompaniment to the revelation of the cross as the SECRET of God's good news. THAT'S why Paul calls his DISTINCTIVE MESSAGE both "the gospel of the grace of God"(Acts 20:24) AND "the preaching of the cross" (1 Cor. 1:18), for the "gospel of the grace of God" IS "the preaching of the cross", as GOOD NEWS. IT is the proclamation of the OVER-ABOUNDING GRACE OF GOD TO MAN THROUGH THE SHED BLOOD OF CHRIST, and in Paul's epistles EVERYTHING CENTERS IN THE CROSS.
According to Paul, through the Holy Spirit, "we have REDEMPTION THROUGH HIS BLOOD"(Eph. 1:7), we are "JUSTIFIED BY HIS BLOOD" (ROm. 5:9), "RECONCILED TO GOD BY THE DEATH OF HIS SON"(ROm.5:10), "MADE NIGH BY THE BLOOD OF CHRIST"(Eph. 2:13) and "MADE THE RIGHTEOUSNESS OF GOD IN HIM" because "GOD HATH MADE HIM TO BE SIN FOR US" (2 Cor. 5:21).
BUT, we MUST be careful NOT TO ASSUME that PREDICTIONS concerning the crucifixion are the SAME AS "the preaching of the cross" or that "the preaching of the cross" has nothing to do with the mystery simply because the crucifixion itself was prophesied.
PREDICTIONS concerning the DEATH OF CHRIST are to be found in NUMEROUS OT passages AS WELL AS in the FOUR RECORDS of CHRIST'S EARTHLY MINISTRY. But NEVER, repeat,NEVER WERE THE MERITS OF CHRIST'S DEATH PROCLAIMED AS THE GROUND OF SALVATION UNTIL PAUL.The difficulty is that SO much has been READ INTO Scripture which is NOT THERE. SEE PETER'S PENTECOST SERMON FOR A GREAT ILLUSTRATION OF THIS.
John the Baptist NEVER proclaimed the merits of Christ as the Lamb of God, bearing away the sin of the world as the ground of salvation. If he knew that, why was his call "repent and be baptized for the remission of sin"? Nor did the 12. Even AFTER the crucifixion, the apostles did NOT immediately see the death of Christ as the SECRET OF THE GOSPEL. Peter REFERRED to the crucifixion, but he DID NOT OFFER IT FOR SALVATION. He BLAMED his hearers for the death of Christ and DEMANDED REPENTANCE AND WATER BAPTISM FOR THE REMISSION OF THEIR SINS (Acts 2:3638).
Philip did NOT preach the cross to the eunuch as the SECRET OF THE GOSPEL. The eunuch had been reading Isa. 53. Philip then PREACHED Christ from that passage, proving from it that the crucified Jesus was indeed the Messiah, whose coming Isaiah had predicted. Read it carefully. NOWHERE does it say that Philip instructed the eunuch that CHRIST HAD DIED FOR HIM, or that the eunuch should TRUST IN HIS DEATH FOR SALVATION. Philip simply identified Jesus as Messiah from that passage, and baptized the eunuch when he confessed: "I believe that Jesus Christ is the son of God" (Acts8:37).
And while you're reading, go back an read ONCE AGAIN Peter's Pentecost message. And find where HE PREACHED the cross as the means of remission of sin and salvation.
Whereas Peter at Pentecost had ACCUSED his hearers of crucifying Christ and had DEMANDED repentance and baptism FOR THE REMISSION OF SINS (Acts2:23,36,38), Paul proclaimed the crucifixion of Christ AS GOOD NEWS (1 Cor. 1:18) and revealed that His death was our remission of our sins. WIth Peter at Pentecost it was a matter of SHAME; Paul GLORIED in it (Gal. 6:14).
Paul, the chief of sinners, saved by grace, OFFERS the cross as the SOLE GROUND OF REMISSION OF SINS(ROm.3:24).
The simple fact is that it was not UNTIL PAUL that Christ's death for sin was proclaimed as GOOD NEWS and seen as the SECRET of ALL the GOOD NEWS that had gone before.
The FACT of Christ's death for the sins of others was "testified beforehand"(1 Pet. 1:11), but Paul, by REVELATION, makes it VERY CLEAR that the ETERNAL PURPOSE OF GOD IN THAT DEATH and the OFFER OF SALVATION TO ALL THROUGH ITS MERITS WAS TO BE:"...TESTIFIED IN DUE TIME, whereunto I am ordained a preacher, and an apostle..."(1 Tim. 2:6,7).
God’s Grace is also spoken of in Acts 11:
Acts 11:19-23 NASB
So then those who were scattered because of the persecution that occurred in connection with Stephen made their way to Phoenicia and Cyprus and Antioch, speaking the word to no one except to Jews alone. But there were some of them, men of Cyprus and Cyrene, who came to Antioch and began speaking to the Greeks also, preaching the Lord Jesus. And the hand of the Lord was with them, and a large number who believed turned to the Lord. The news about them reached the ears of the church at Jerusalem, and they sent Barnabas off to Antioch. Then when he arrived and witnessed the grace of God, he rejoiced and began to encourage them all with resolute heart to remain true to the Lord;
I will add Isaiah 53 is the very definition of God’s Grace:
Isaiah 53:1-12 NASB
Who has believed our message? And to whom has the arm of the L ord been revealed? For He grew up before Him like a tender shoot, And like a root out of parched ground; He has no stately form or majesty That we should look upon Him, Nor appearance that we should be attracted to Him. He was despised and forsaken of men, A man of sorrows and acquainted with grief; And like one from whom men hide their face He was despised, and we did not esteem Him. Surely our griefs He Himself bore, And our sorrows He carried; Yet we ourselves esteemed Him stricken, Smitten of God, and afflicted. But He was pierced through for our transgressions, He was crushed for our iniquities; The chastening for our well-being fell upon Him, And by His scourging we are healed. All of us like sheep have gone astray, Each of us has turned to his own way; But the L ord has caused the iniquity of us all To fall on Him. He was oppressed and He was afflicted, Yet He did not open His mouth; Like a lamb that is led to slaughter, And like a sheep that is silent before its shearers, So He did not open His mouth. By oppression and judgment He was taken away; And as for His generation, who considered That He was cut off out of the land of the living For the transgression of my people, to whom the stroke was due? His grave was assigned with wicked men, Yet He was with a rich man in His death, Because He had done no violence, Nor was there any deceit in His mouth. But the L ord was pleased To crush Him, putting Him to grief; If He would render Himself as a guilt offering, He will see His offspring, He will prolong His days, And the good pleasure of the L ord will prosper in His hand. As a result of the anguish of His soul, He will see it and be satisfied; By His knowledge the Righteous One, My Servant, will justify the many, As He will bear their iniquities. Therefore, I will allot Him a portion with the great, And He will divide the booty with the strong; Because He poured out Himself to death, And was numbered with the transgressors; Yet He Himself bore the sin of many, And interceded for the transgressors.