The emphatic declaration of 2 Tim.3:16 is: "ALL SCRIPTURE is given by INSPIRATION OF GOD…" The word, "inspiration", means "God-breathed". God the Holy Spirit influenced certain men, at various times, to write down his very words, and ONLY his words. In some mysterious way, the Holy Spirit moved men to write down the very WORD of the living God. Another important passage of Scripture in this regard is 2 Pet.1:20,21: "Knowing this first, that no prophecy of the scripture is of any private interpretation. For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost." The Holy Scriptures did not originate with men, but with the Holy Spirit. And he "moved" men to speak (and write) his Word. They wrote under his influence.
Now, it is very important to understand that these men were not writing as if they were mindless robots, or in a trance-like state. No; any reading of the Bible soon reveals that each human instrument used had his own style, etc. The Lord made use of each one's particular talents, abilities, etc. And yet, the Holy Spirit so controlled those men, that EVERY SINGLE WORD they spoke or wrote, while being "moved" by the Holy Spirit, was what God wanted them to write! Though the Lord used them as his instruments, HE was the Author of all Scripture. Their faculties were employed, but the words were the Lord's.
And this the Scriptures themselves declare to be the case. "The words of the LORD [note that – not the words of man, but of the Lord] are pure words" (Psa.12:6). Which words? "EVERY WORD of God is pure" (Prov.30:5). "ALL scripture is given by inspiration of God"!
How highly the Lord magnifies his Word is seen in Psa.138:2: "thou hast magnified thy word above all thy name"! That being so, it is perfect and infallible; each word is from God – not one originated with man. In fact, so marvellous is this divine Book, that inspiration extended, not only to every word, but even to every "jot" and "tittle" (Matt.5:18)!
Many other passages could be given which throw light on this blessed subject. Here are just a few of them.
Exod.24:4 says, "And Moses wrote all the words of the LORD." Here we find that, although Moses was the man the Lord used to actually put the words down in writing, they were not Moses' words, but "the words of the LORD"! And the people understood this clearly, for they said, "All that the LORD hath said [not Moses, but the Lord] will we do, and be obedient" (vs.7).
In 2 Sam.23:1,2, we have the express words of David, who declared that: "The Spirit of the LORD spake by me, and his word was in my tongue." Here is a plain testimony to divine inspiration! Yes, David's mouth was used; his tongue was employed; but the word he spoke was the LORD'S Word, not his!
The prophet Jeremiah, also, testified plainly to divine inspiration. He wrote, "Then the LORD put forth his hand, and touched my mouth. And the LORD said unto me, Behold, I have put my words in thy mouth" (Jer.1:9). Jeremiah's mouth – but God's words!
And then, the words these prophets spoke, were later written down. Here is an example of how it was done: "And it came to pass in the fourth year of Jehoiakim the son of Josiah king of Judah, that this word came unto Jeremiah from the LORD, saying, Take thee a roll of a book, and write therein all the words that I have spoken unto thee against Israel, and against Judah, and against all the nations, from the day I spake unto thee, from the days of Josiah, even unto this day" (Jer.36:1,2). The words spoken by divine inspiration were later written down by divine inspiration.
The Bible is full of testimonies such as these. We have the infallible testimony of the Lord Jesus Christ himself. He declared, for example, that David spoke "by the Holy Ghost" in the Psalms (Mk.12:36). The Son of God cannot lie. As for his own words, he stated that they were from the Father (Jn.17:8).