You sure added a lot of words PAUL did NOT say ! Paul taught that the mystery was revealed to the Apostles and the Prophets by the SPIRIT.
JohnW rightly noted some passages that bring out one intended sense of two, that apply. Steko touched on the other one...
Case in JohnW's point....
Acts 14:14 Which when the apostles, Barnabas and Paul, heard of, they rent their clothes, and ran in among the people, crying out,
Barnabas was considered an Apostle.
And there were other BODY Apostles one can find being mentioned in other passages...
But the other equally valid sense of Ephesians 3:5's "as it is now revealed unto his holy apostles and prophets by the Spirit;" is in described the following...
Galatians 2:1 Then fourteen years after I went up again to Jerusalem with Barnabas, and took Titus with me also. 2:2 And I went up by revelation, and communicated unto them that gospel which I preach among the Gentiles, but privately to them which were of reputation, lest by any means I should run, or had run, in vain.
2:7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter; 2:8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles: ) 2:9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
James, Cephas and John had been led to perceive or understand some things, through Paul's words to them.
And it did not end there, for copies of Paul's writings were somewhat distributed to the various groups and assemblies...
2 Peter 3:15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you; 3:16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
Note: Peter is NOT saying that HE does not understand those things the Spirit had confirmed to him as to the validity of those things Paul wrote of.
Rather; that those who are unlearned in those things, and as a result are not established in an understanding of them (are unstable), twist them into some other intended meaning; just as some were then doing with the Law and the Prophets (the topic Peter began the chapter with).
Note: Paul had written of the Lord's delay once more - in His longsuffering - which is part of what Peter is talking about to his direct readers (see, for example, Romans 9-11, in light of Romans 1:18-3:30).
How were Paul's words confirmed unto them by the Spirit?
Acts 15:12 Then all the multitude kept silence, and gave audience to Barnabas and Paul, declaring what miracles and wonders God had wrought among the Gentiles by them.
That had been the Spirit's recurrent pattern throughout the earlier part of Paul's ministry...
Romans 15:16 That I should be the minister of Jesus Christ to the Gentiles, ministering the gospel of God, that the offering up of the Gentiles might be acceptable, being sanctified by the Holy Ghost. 15:17 I have therefore whereof I may glory through Jesus Christ in those things which pertain to God. 15:18 For I will not dare to speak of any of those things which Christ hath not wrought by me, to make the Gentiles obedient, by word and deed, 15:19 Through mighty signs and wonders, by the power of the Spirit of God; so that from Jerusalem, and round about unto Illyricum, I have fully preached the gospel of Christ. 15:20 Yea, so have I strived to preach the gospel, not where Christ was named, lest I should build upon another man's foundation: 15:21 But as it is written, To whom he was not spoken of, they shall see: and they that have not heard shall understand.
The signs of an Apostle were how Paul's words and ministry were confirmed as being from God.
2 Corinthians 12:12 Truly the signs of an apostle were wrought among you in all patience, in signs, and wonders, and mighty deeds.
Note: Romans 15:21 is Paul's application of the OT in a manner unique to him (and two other individuals in Scripture).
He will quote an OT passage, not as an assertion that it is being fulfilled in his day, but in his application of an operating principle within such passages, that is
"the same" in operating principle in said OT passage
"but different" in his unique application of it in his day.
That alone throws many off as to where Paul is often actually coming from.
Only three people in Scripture are able to do that - Moses; Paul; and the Lord - Who ALONE IS the foundation upon which both men had each been given their unique, distinct - foundational - calling.
Moses the LORD's Great Law Dispenser, and Paul; the Lord's Great Mystery Grace Dispenser.
