Before you ask that question, you'd better first ask how you know whether any book in your New Testament is really canonical Scripture. There's no inspired, apostolically-endorsed table of contents. If your only authority is what's written in the Scriptures, your authority for knowing that 2 Thess or 1 Cor is scripture at all rests on ... nothing.
Christ didn't give teaching authority to a book, and never commanded the writing of a single verse of the NT. He gave teaching authority to his disciples in the Great Commission, and 2 Tim 2:2 tells you that they passed that teaching authority on to those who came after them.
By the way ... what does the Bible call "the pillar and ground of the truth"?
It is clear that Christ and the Apostles treated Scripture as authoritative and as constituting truth. The question that now needs answering is, "Are the Scriptures we possess today worthy to be treated as Christ treated them?" We know that through the historical redemptive events Scripture was "breathed of God." This applies to the originals and not to copies of them. The original was made by men moved by the Holy Spirit. The copies were made by ordinary men. But does this fact mean a great loss to us? Are our present-day copies so poor that they are not trustworthy? When one realizes that God revealed His plan of redemption to men through historical events, and that we know about these events only through Scripture, one will also realize that these Scriptures must be trustworthy. Otherwise we would not know of His plan of redemption. It is beyond one's imagination that an infallible and loving God would let His plan of redemption be lost through untrustworthy copies of the Scriptures. Also, when one realizes that God prevented errors from entering the originals by guiding the writers by the Holy Spirit, one will realize that God would also have prevented significant errors from entering through copying.
One's confidence in our Scriptures is also supported by the attitude of Christ and the Apostles toward them. They did not hesitate to trust the Old Testament Scriptures. These too were not originals. If they had faith in the adequacy of their copies and never questioned them, we should have even more faith in our New Testament copies as being trustworthy.
Many of the copies we possess are bound to contain errors due to the numerous copyings and recopyings they have gone through. Although the copying process did introduce a few errors, it also increased the means for finding errors. By careful study and comparison of the many old manuscripts, it is possible to obtain a sound proximity of the originals. The errors that were introduced here and there in some of the copies are found by comparing the many manuscripts, making it possible to approximate the original. This approximation of the original can be considered as inerrant and infallible; that is, it can be held as a reliable authority (never deceiving or misleading) and is free from error (always giving the thought of the original). This does not necessarily mean that we have a slavish verbatim copy of the original down to every small word. There might be trifling variations in wording. But these are so minor that there is no doubt about the authors' thoughts not being known to us, and in most cases there is little doubt about now knowing the words they used to communicate the thoughts.
>> “the pillar and ground of the truth”?<<
What was the Church to teach? Something other then what is found in Scripture?