When was divine inspiration of the NT first explicitly affirmed?

Question

I was recently reading Hebrews 3:7 and was struck by how remarkble it is that the author attributes Psalm 95 directly to the Holy Spirit. Similarly, Hebrews 1 attributes many other OT passages to God directly. And most famously, 2nd Timothy 3:16 says that all Scripture (presumably referring to the OT) is "God-breathed".

Modern Christians (including myself) of most denominations would be perfectly comfortable saying similar things of the NT, either that it is divinely inspired or quoting it as "the Holy Spirit says..." I am wondering, when was this belief in divine inspiration of the NT explicitly stated? To be clear what I mean by "explicit", I am not referring to the inference that might be made from 2nd Peter 3:16 and 1st Timothy 5:18 calling other parts of the NT "Scripture". I am also not referring to the belief that the quotations of Jesus are spoken by God, as that would be an affirmation of his divinity (or at the very least, his status as a prophet) and not of the divine origin of the Bible itself.

I am looking for some instance where a Christian writer expressly says that some part of the New Testament was spoken by God or the Holy Spirit, when (in context) it is not a quotation from God, Jesus, or the Holy Spirit. Something akin to the example either of Hebrews 3:7 with a specific statement, or 2nd Timothy 3:16 with a blanket declaration of divine origin and authority for some or all of the NT.

Edit in response to some confusion: This is a historical question, not a theological question. I am not asking whether the NT is inspired, nor am I asking what in the NT leads the reader to believe that, but rather I am asking when (that we have direct evidence of) this inspiration was first recognized.

Answer 1

Apart from the NT itself, we have early declarations that NT (and OT) Scripture is divinely inspired.

Irenaeus

We have learned from none others the plan of our salvation, than from those through whom the Gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith. Irenaeus Against Heresies Book III Chapter 1 Verse 1

Irenaeus wrote circa 175. Though not using the same exact words of divinely inspired, it is clear enough that Scripture being the ground and pillar of our faith admits to its divine Source.

Clement of Alexandria

But those who are ready to toil in the most excellent pursuits, will not desist from the search after truth, till they get the demonstration from the Scriptures themselves. ... For we have, as the source of teaching, the Lord, both by the prophets, the Gospel, and the blessed apostles, “in divers manners and at sundry times,”3670 leading from the beginning of knowledge to the end. ... For those are slothful who, having it in their power to provide themselves with proper proofs for the divine Scriptures from the Scriptures themselves, select only what contributes to their own pleasures. The Stromata Book VII Chapter XVI

Clement of Alexandria wrote circa 200. He calls Scriptures divine, including the OT and NT.

Origen

And that this testimony [of Holy Scripture] may produce a sure and unhesitating belief, either with regard to what we have still to advance, or to what has been already stated, it seems necessary to show, in the first place, that the Scriptures them­selves are divine, i.e., were inspired by the Spirit of God. We shall therefore with all possible brevity draw forth from the Holy Scriptures themselves, such evidence on this point as may produce upon us a suitable impression, (making our quotations) from Moses, the first legislator of the Hebrew nation, and from the words of Jesus Christ, the Author and Chief of the Christian religious system. Origen on Principles Book IV Chapter 1 Verse 1

He then develops this assertion through the remainder of his letter by quoting prophecy OT and fulfillment NT, among other proofs. Origen wrote circa 225.

So, the belief that NT Scripture, and OT Scripture, is divinely inspired sources to the very beginnings of Christianity.

Answer 2

One of the earliest, and most reliable Christian writers we have, wrote this about what became known as the last book of the New Testament. This writer had spent years with Jesus Christ himself, before his visible ascension back to heaven, and was much loved by Jesus. The writer wrote the following, which are his words, not those of Christ, or of God:

"The Revelation of Jesus Christ, which God gave unto him, to shew unto his servants things which must shortly come to pass; and he sent and signified it by his angel unto his servant John [the Apostle, who then wrote down the message conveyed to him.]

Who bare record of the word of God, and of the testimony of Jesus Christ, and of all things that he saw. Blessed is he that readeth, and they that hear the words of this prophecy, and keep those things which are written therein: for the time is at hand. John to the seven churches which are in Asia..." Revelation 1:1-4 A.V.

It is not until verse 8 that John starts giving a verbatim report of all that was given to him, to hear and to see, by the angel sent from the resurrected Christ. Then, at the close of the book, John writes these words of his own which would convince Christians like Irenaeus, and Clement of Alexandria that all that had been written was truly inspired of the Holy Spirit:

"Even so, come, Lord Jesus. The grace of our Lord Jesus Christ be with you all." (vss. 20-21)

Now, why would those closing two sentences convince those Christians? Because, by the time they wrote their affirmations of the New Testament (circa 175-200) the prophecies recorded by the Apostle John were clearly in process of happening. Nearly 100 years later, the Church was suffering the persecutions the Holy Spirit had inspired John to write about. And the hearts of believers were aching (as had John's heart) to see Christ return in glory, as that book foretold. They all believed that Christ would suddenly, and spectacularly appear to deliver his people from the build-up of horrors that were foretold. Even though some Christians had doubts about that particular book of the New Testament, in time it became very clear that this was no hallucination of John's, but had been inspired of the Holy Spirit, and so that writing was included as holy writ.

The question asks when divine inspiration of the NT was first explicitly affirmed, but rules out the affirmations contained within those writings. Does this mean that only the opinions of men who lived some 100 years after the last of those writings is to be taken as authoritative, superseding the authority of the very Holy Spirit-inspired words written? That might make for a good follow-up question.