Please consider these three passages of Scripture
Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us,
Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the word;
It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order, most excellent Theophilus,
That thou mightest know the certainty of those things, wherein thou hast been instructed.
Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints.
Whereby, when ye read, ye may understand my knowledge in the mystery of Christ
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;
That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Pauline revelation is not superior to other revelations through other apostles in the New Testament
Although so much was revealed to Paul, that does not in any way make what was revealed to others inferior.
It is only still a part of the whole package!
All are scriptures given by the inspiration of the Holy Spirit and are profitable to us for the doctrine of salvation and for instruction in righteousness.
When someone starts saying any part of any of the epistles was written to unbelievers or that some truth in the new testament was meant for those in the old testament
That’s how errors begin
For instance, there is absolutely nothing that suggests that the first chapter of 1st John was written to unbelievers.
Some try to ignore the fact that “we” was used by John throughout that chapter
Because that would mean John was also an unbeliever.
The truth is, all of John’s letters were written to believers and are the truth of God’s word as written.
One sure way of knowing that a teaching is extreme is when the teacher tries to reduce or diminish any part of the truth of God’s word.
Every Bible teacher must be careful not to do this.