Rom. 16:25, Eph. 3:9, and Col. 1:26: "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" (ROm. 16:25); "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. 3:9); "Even THE MYSTERY which hath been HID FROM AGES AND GENERATIONS, but NOW is made MANIFEST to his saints" (Col. 1:26).
There is a GREAT DIFFERENCE between that which was "SPOKEN by the mouth of all [God's] holy prophets since the world began" and that which was "KEPT SECRET since the world began".
You might want to re-think your position on this, since it FLIES in the face of what God has CLEARLY stated.
Titus 3:9 But avoid foolish questions, and genealogies, and contentions, and strivings about the law; for they are unprofitable and vain...
It isn't the WHAT, it's the HOW. Perhaps you had missed this part:
Amo_3:7 Surely the Lord GOD will do nothing, but he revealeth his secret unto his servants the prophets.
and this:
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.
pssst! at the sound of the seventh trumpet, the mystery is finished!
See, the thing is, the whole POINT of the prophecy is to declare what He is doing from the beginning - that is what proves he is God. Messiah is not a mystery - He is in the OT. The church is not a mystery - it is in the OT. The gentiles being brought in? OT.... The rapture? OT.
The way one knows that a thing is from YHWH is to SEARCH THE SCRIPTURES - If it ain't in the scriptures, it ain't from YHWH, Right? And what were the scriptures in Paul's day? OT. It HAS to be found in the beginning if it is of YHWH, because NOTHING can be added to or taken from...
Just how is it that folks are supposed to confirm Paul in his day without the Scriptures? How is this 'new' thing to be reckoned?