keep these things a secret back then for had He revealed them when they were written Satan and his principalities would not have had our Lord crucified.  And had our Lord not been crucified then we would have all gone to hell for it's in His crucifixion that He paid for the sins of man.  And so we find Paul saying concerning "his gospel" after our Lord's death, "BUT NOW is made manifest and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith" (Rom. 16:26).  Please observe the words "But now" in the passage.  It's only "BUT NOW" the Bible says that God is willing to reveal these truths concerning His Son's death for men's sins.  Notice how it was that He revealed them.  It was by His Spirit through the ministry of the apostle Paul that they were now to be made manifest and Paul also said it was "by the scriptures of the prophets" that they were now made known to all nations for the obedience of faith.  It was Paul through the leadership of the Holy Spirit who now reached back into the Old Testament scriptures and showed that God would be sending His Son to die for--and he said--"our sins according to the scriptures" (I Cor. 15:3).  There were only certain ones' sins to which the Lord had promised in the Old Testament that Christ would be dying for.  According to Isaiah he said, He would be "wounded for our transgressions" (Isa. 53:5).  The "our transgressions" of verse 5 would be the nation of Israel and whosoever blessed the seed of Abraham according to the covenant of Genesis 12:3.  So it is with Isaiah's prophecy in Chapter 53 Verse 6.  Isaiah said: "All we like sheep have gone astray; we have turned every one to his own way; and the Lord hath laid on Him the iniquity of us all."  The "us all" of the verse could be none other than the nation Israel and those that blessed them.  Mark well, the Bible says in Isaiah Chapter 53 towards the end of Verse 8, "…for the transgression of my people was He stricken."  Please observe the words "my people" in the text.  It was not just anyone's sin that Christ would be dying for according to the scriptures of the prophets.  Rather, it was for God's people.  Notice also at the end of verse 12 in Isaiah Chapter 53.  It says: "…and He bare the sin of many, and made intercession for the transgressors."   Isaiah did not say that He would bare the sin of all, he says He would bare the sin of many.  There is a big difference in MANY and ALL.  This, no doubt, now explains our Lord's words at the Last Supper when He said the following concerning the blood of the New Testament to be shed.  Notice very carefully.

             "For this is the blood of the new testament, which is shed for many for the remision of sins" (Matt. 26:28).

Please notice that it doesn't say that Christ's blood would be shed for ALL where the New Testament is concerned, it says it was to be shed "for many" (Matt. 26:28). 

Now back to Paul. Paul's gospel was a mystery, which was kept secret or hid back in the Old Testament scriptures only for certain men to later know and read about through Paul's preaching.  This is why we find the apostle doing things the way that he did them in the book of Acts.  For instance, the Bible says in Acts 17:1-3 the following.