Col 1:27 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
The Apostle Paul’s epistles and the other epistles and gospels of the New Testament, have to be viewed in light of the mystery of God and when it was revealed, and the impact this has on how the church perceives salvation. Paul at a certain point in his ministry, wrote of a revelation he received from God.
Eph 3:3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
6 That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Paul was given the dispensation to fulfill, fill up, the word of God by disclosing the mystery of Christ, to the church, Col 1:25. At what point in time this revelation was given to Paul, is not really made clear in the epistles. Using the search function in a bible editor, one can examine the scriptures used in connection with the word mystery, related to the mystery of God, and get a rough idea when Paul received this revelation. The mystery is most clearly defined in Paul’s later epistles of Ephesians and Colossians. We find that this mystery was hid in God since the beginning of the world, Eph 3:9, and was only made manifest to the saints at a specific point in time, Col 1:26. The mystery of God, which is Christ in you the hope of glory, is finished at the sounding of the seventh trumpet.
Revelation 10:7 KJVS
 But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.
That is when the head of the body is joined to the body of Christ. When every member of the body of Christ receives their glorified body. The hope of glory, that the members of the body of Christ are in expectation of, is to rule and reign with Jesus Christ during the thousand year kingdom of God. God’s glory on this earth. Since being sanctified and becoming perfect or mature are words associated with the mystery of God, when and where these words appear in scripture can tell us much. The word sanctify, and its derivatives, as they appear in the New Testament, gives us some idea when the mystery of God first became known to the church. Books written before the disclosure of the mystery of God lack any information concerning sanctification, which is accomplished by Christ in you, Jn 17:17, 19&23. The authors who wrote epistles or gospels before Paul received this revelation were either not aware of the mystery or were not inspired to mention the mystery at the time when they wrote the epistle or gospel. The epistle written by James reflects this lack of knowledge regarding the mystery of God and the role Christ in you, plays in being sanctified. Sanctify and other derivatives of that word, in connection to the body of Christ, appears in the gospel of John, in later chapters of Acts and then in Ro 15:16, in the order the gospels and other New Testament books as they appear in the bible. The gospel of John is thought to be written in the 80’s or early 90’s. John 17:17&19&23, reflect the knowledge of the mystery of God in Christ. The first time the mystery of God was briefly mentioned by Paul was in Ro 16:25. I feel, contrary to what some believe, that Romans was written before the first Corinthian epistle. I will give my reason why, in just a bit. The concept of sanctification is contingent upon Christ in you the hope of glory. Sanctification and the mystery are briefly touched upon by Paul in the 15th and 16th chapters of Romans, and commented upon twice in the 1st Corinthian epistle, once in the beginning verses, 1Co 1:2, and in 1 Co 6:11
1Co 6:11 And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
Sanctification takes place due to the offering of the body of Jesus Christ once for all, Heb 10:10. So when Paul remarks in Ro 15:16 that the offering up of the Gentiles might be acceptable, being sanctified by the Holy Ghost, this knowledge is contingent upon the revelation of the mystery of Christ in you the hope of glory. Since there is only one offering for sin connected with sanctification, He 10:14, then the offering up of the Gentiles mentioned in Ro 15:16 has to be understood as taking place”in Christ”. Because there can be no sanctification without being in the corporate body of Christ, and having God and Christ dwelling in you.
John 17:23 KJVS
 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
Hebrews 2:11 KJVS
 For both he that sanctifieth and they who are sanctified are all of one: for which cause he is not ashamed to call them brethren,
In Ephesians 3:3, Paul refers to the mystery and that he had mentioned it before in a few words. A reference bible links this verse to Ro 16:25. That clearly puts a rough time stamp on when the mystery was disclosed to Paul. A important point supporting the premise that the epistle to the Romans was written before the Corinthian epistles, is when Paul makes two similar utterances by the Spirit, in Romans and then 1 Corinthians. In both verses Paul asks the question, “who has known the mind of the Lord?”, Ro 11:34, 1Co 2:16. But in the 1 Corinthians verse, a observation is made following that question, in which Paul states that we have the mind of Christ! Having the mind of Christ is only possible by having the Christ in you, the hope of glory. So why did Paul not make that observation in Ro 11:34? Obviously because the Spirit did not inspire Paul to include that comment in Romans or perhaps he had not received the revelation of the mystery of Christ in you the hope of glory, until he was nearly finished with the writing of the book of Romans. And then only briefly touch upon it in Ro 16:25. All this is speculative but the books of 1&2 Corinthians have more content regarding being sanctified and being in the body of Christ than the book of Romans does. My guess is, this may be due to progressive revelation by the Holy Spirit. Christ in you the hope of glory, and the sanctification of the Gentile members of the body of Christ, along with the Hebrew contingent, was not touched upon in the gospels and epistles written earlier in time before Paul received the revelation of the mystery. Probably for a few important reasons. The early church was facing the hurtle of establishing in the Jewish believer’s minds, that one could not be justified by one’s own works under the law but by grace. Which came about due to the redemptive work of salvation by Jesus Christ. God instructs man on a individual and societal basis and uses the church in these functions. The Jewish culture had been waylaid by their religious leaders and mislead in believing they could be justified by the law. The law was added in the wilderness, due to transgression, Ga 3:19, and made no one perfect, He 7:19. Perfect or mature is another word that describes the process of being sanctified, due to Christ in you. The Pharisees and other religious leaders in Israel stumbled at the stumbling stone, which God laid, the rock of offense, Ro 9:31-33, who was Jesus Christ. They were intent on establishing their own righteousness by observing the law of Moses and their own doctrines of man. This type of self will worship is insidious and was something God had ordained for them to follow, 1Pe 2:8 , Ro 9:22. The emerging Jewish Christian church was having a hard time making the transition from the law of Moses to living a life of faith and being justified by grace, via the Holy Spirit. This was so much of a culture shock, that even Apostle Peter fell back into old patterns of behavior in regards to the law and separation of Jews and Gentiles, Ga 2:12-14. Another consideration is that the early Jewish Christian church was persecuted by the leadership of Israel and the Levitical priesthood had considerable knowledge concerning prophecy and the Old Testament scriptures. If they had found out very early on about the mystery of Christ in you the hope of glory, ultimately leading to sanctification of the Jewish and Gentile Christians, they very well may have not crucified the Lord.
1 Corinthians 2:7-8 KJVS
 But we speak the wisdom of God in a mystery, even the hidden wisdom , which God ordained before the world unto our glory:  Which none of the princes of this world knew: for had they known it , they would not have crucified the Lord of glory.
Verse 7 added additional information that this mystery and hidden wisdom of God was ordained by God unto our, the body of Christ, glory.
Apostle Paul by prophecy points to when this takes place.
1 Corinthians 15:43,51-52 KJVS
 It is sown in dishonour; it is raised in glory: it is sown in weakness; it is raised in power:  Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,  In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
Timing played a big part in when the release of the revelation of the mystery of God was released. The fledgling Christian church faced much opposition from the Jewish leadership early on and perhaps that has bearing on when the mystery of God was disclosed to the church. It was a profound example of the power of God over the will of man, to convert Saul to the faith of Jesus Christ, who just seconds before was extremely zealous in stamping out the Jewish Christian church. And chose him to be the Apostle to the Gentiles. There were Old Testament prophecies of salvation being taken away from Jews and given to the Gentiles, Deut 32:21, Isa 65:1. If you read the parable of the husbanmen, Mt 21:33-45, it was clear to the chief priests that Jesus was indicating that the kingdom of God would be taken away from them and given to the nations or Gentiles. The Apostle Paul proclaimed this very fact in Ac 28:25-28, again quoting a Old Testament prophet. The chief priest were afraid of losing their place of power over Israel and that was largely why they crucified Jesus.
Joh 11:48 If we let him thus alone, all men will believe on him: and the Romans shall come and take away both our place and nation.
When the time arrived that salvation went to the Gentiles the Jewish leadership did not want the gospel preached to the Gentiles
1Th 2:15 Who both killed the Lord Jesus, and their own prophets, and have persecuted us; and they please not God, and are contrary to all men:
16 Forbidding us to speak to the Gentiles that they might be saved, to fill up their sins alway: for the wrath is come upon them to the uttermost.
So when the Apostle Paul in 1 Co 2:6-8 states what appears to be obvious, albeit after the fact, that if the princes of this world had known about the mystery of God, they would not have crucified the Lord. This is a very important fact in regards to progressive revelation. Unless a seed fall in the ground and die it cannot bring forth any fruit, Jn 12:24, which is a perfect parable used by our Lord describing his sacrifice and offering and his role as the seed, the Christ in you the hope of glory. But Jesus spoke in parables to disguise the real intent behind God sending him to earth as a sacrifice and offering for sin, Mk 4:11. God on the macro scale was and is changing society and on the individual, micro scale, changing individual men within the different societies. The transition from law to grace, the transition from Jew to Gentile in regards to salvation was a very difficult cultural transition for the early church to pass through. God is a excellent card player and holds His cards very close to His chest and plays the cards of history and the salvation of mankind through Jesus Christ, Jn 12:32, in the order that pleases Him, Isa 46:8-10. Not only within society but also within our individual lives. It is interesting to look at the three different accounts Paul gives in the book of Acts in relationship to time, regarding his experience on the road to Damascus. In the different accounts Paul discloses what Jesus said to him at that time, and how these various accounts differ as recorded in the book of Acts, is interesting. The verses being examined are Acts 9:4-6, Acts 22:7-10 and Acts 26:14-18. It is only in Acts 26:18 that the word sanctified is mentioned and that is in regards to inheritance. That word sanctified is used only one other time in Acts, in verse 20:32. Again in regards to inheritance. As I wrote earlier, in the four gospels the word sanctified, in regards to the body of Christ, is only mentioned in the gospel of John. The following verses have always had a profound effect on me.
John 17:19-23 And for their sakes I sanctify myself, that they also might be sanctified through the truth.
20 ¶ Neither pray I for these alone, but for them also which shall believe on me through their word;
21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one:
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
I in them, and thou in me, that they may be made perfect in one, is a apt description of sanctification, He 10:14. The gospel of John was thought to be written in 90 A.D., and for that reason is the most theological mature gospel. Which is a prime example of progressive revelation in itself. The point being made, is that sanctification, Christ in you the hope of glory, was a concept disclosed by God to the world and to the church, in the time frame He saw fitting. First, the transition from the law to grace in regards to who justifies who, man justifying himself or God justifying man, had to be firmly established. Then the first order in the salvation process of mankind is address, the body of Christ being justified and then sanctified through the offering of the body of Christ once for all, He 10:10, He 13:12. It takes time in order to change society and the individuals who are indoctrinated by the doctrines of men, who live in those societies. Living a life under the law, mistakenly trying to justify your self before God by your own efforts. Living lives as pagans sacrificing to idols and demons. The transformation taking place in society and in the individuals at that time, and even today, by those called of God, was and is enormous. One also has to keep in mind that these changes in society and in the individual are linked hand in hand with the educational process of being taught by God, Jn 6:45. The knowledge of good and evil, which makes us like God, Ge 3:22, and discernment thereof, can only be learned by experience, He 5:14. This all gives a person just a glimmer of understanding of the work God is doing in this earth, Acts 13:41. Keep in mind that in the salvation process of mankind, 1Ti 4:10, God will eventually justify all men by His grace, through the redemption that is in Christ Jesus. In regards to sanctification, God is sanctifying Himself a people, He 13:12, and the body of Christ, for a inheritance to rule and reign with Jesus Christ in the age to come, Eph 1:11, Col 1:12. That sanctification can only happens by the offering of the body of Jesus Christ once for all. Which is the mystery of God in Christ, the Christ in you the hope of glory.