Col 1:25 Whereof I am made a minister, according to the dispensation of God which is given to me for you, to fulfil the word of God; 26 Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints: 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:
There is a mystery which was hid from ages and generations, and the riches of this mystery is Christ in you, the hope of glory.
We learn throughout the New Covenant that there was a mystery, it was hidden, kept secret, it was ordained to our glory; all shall share in the fellowship and be gathered together in one in Christ Jesus.
These mysteries were not known before and Jesus spoke in parables to keep them hidden from those who were not of his followers: Matt 13:11; Mark 4:11; Luke 8:10 to you it is given to know the mysteries of the kingdom of Heaven, but to the rest I speak in parables.
See below gathered scripture references on this mystery. This is augmented when you begin to look as well at scriptures relating to he oneness in Christ Jesus that we have in this new covenant. (John 17:20-23 and many more)
1 Cor 2:5 That your faith should not stand in the wisdom of men, but in the power of God. 6 Howbeit we speak wisdom among them that are perfect: yet not the wisdom of this world, nor of the princes of this world, that come to nought: 7 But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory: 8 Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory. 9 But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.
1 Cor 4:1 Let a man so account of us, as of the ministers of Christ, and stewards of the mysteries of God.
1 Cor 13:2; 14:2
Rom 11:25 For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
Rom 14:25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began, 26 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: 27 To God only wise, be glory through Jesus Christ for ever. Amen.
Eph 1:9 Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself: 10 That in the dispensation of the fulness of times he might gather together in one all things in Christ, both which are in heaven, and which are on earth; even in him:
Eph 3:2 If ye have heard of the dispensation of the grace of God which is given me to you-ward: 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:
Eph 3:9 And to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ:
Eph 5:31 For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh. 32 This is a great mystery: but I speak concerning Christ and the church.
Eph 6:19 And for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel, 20 For which I am an ambassador in bonds: that therein I may speak boldly, as I ought to speak.
Col 2:2 That their hearts might be comforted, being knit together in love, and unto all riches of the full assurance of understanding, to the acknowledgement of the mystery of God, and of the Father, and of Christ; 3 In whom are hid all the treasures of wisdom and knowledge.
Col 4:2 Continue in prayer, and watch in the same with thanksgiving; 3 Withal praying also for us, that God would open unto us a door of utterance, to speak the mystery of Christ, for which I am also in bonds: 4 That I may make it manifest, as I ought to speak.
1 Tim 3:8 Likewise must the deacons be grave, not doubletongued, not given to much wine, not greedy of filthy lucre; 9 Holding the mystery of the faith in a pure conscience. 10 And let these also first be proved; then let them use the office of a deacon, being found blameless.
1 Tim 3:14 These things write I unto thee, hoping to come unto thee shortly: 15 But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth. 16 And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.
The result of this mystery is stated here:
1 Cor 15:50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption. 51 Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed, 52 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. 53 For this corruptible must put on incorruption, and this mortal must put on immortality. 54 So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality...
In the end we shall all be changed and joined together in the kingdom of God.
There are a few other mysteries mentioned in Revelation
Rev 1:20
Rev 10:7 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.
Rev 17:7