When it comes to the New Testament canon, the authors of the books of the New Testament understood that they were writing with the inspiration of the Holy Spirit.
-  “Which things also we speak, not in the words which man’s wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.’ (1 Corinthians 2:13)
-  “But she is happier if she so abide, after my judgment: and I think also that I have the Spirit of God.†(1 Corinthians 7:40).
They also recognized each other’s books as canonical. For instance, the Apostle Peter recognized the writings of the Apostle Paul as divinely inspired Scripture.
- “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; 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.†(2 Peter 3:15-16)