In the First Vision, when the Lord addressed Joseph, the account tells it in these words:
Or, in other words, Joseph has the Lord borrow from Jude 1: 4: "For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ."
And Isaiah 29: 13: "Wherefore the Lord said, Forasmuch as this people draw near me with their mouth, and with their lips do honour me, but have removed their heart far from me, and their fear toward me is taught by the precept of men."
And from Titus 1: 14: "Not giving heed to Jewish fables, and commandments of men, that turn from the truth."
And 2 Tim. 3: 5: "Having a form of godliness, but denying the power thereof: from such turn away."
Or, the Lord conveyed into the mind of Joseph an indelible impression of truth, which would remain with him and expand and distill as he pondered on its meaning. When at last Joseph was able to set it out in an inspired retelling, the words of scripture flooded into his mind and equipped him to compose an account that would ring with truth, convey what happened, and testify of the authenticity of the words of ancient prophets, while letting the world know what the Lord's message was to Joseph. But the language, even the quotes, are not what transpired. They are an accurate retelling, but reduced to our form of communication. The Lord's manner of telling is quite different. It is unencumbered by our vocabulary, and conveys pure meaning and intent. Therefore Joseph was able to capture and compose the information with power and meaning to us. But to do so Joseph had to resort to scripture.
Which again, begs the question: "Why?" Why do prophets resort to the scriptures to explain the truth as revealed to them? Why does a new revelation get put into the words of an earlier revelation? Why does a stunning new truth come forth as an exposition of the already familiar words of scripture?
In perhaps his greatest sermon, Joseph drew from and expounded on the scriptures to proclaim new doctrines, unheard of by those who had studied the Bible for two thousand years. As he did so he remarked: "It has always been my province to dig up hidden mysteries --new things-- for my hearers. Just at the time when some men think I have no right to the keys of the Priesthood --just at that time I have the greatest right." (TPJS p. 364.) He goes on to expound from the Bible on the true meaning of "eternal judgment" and the resurrection, "salvation for the dead," the plurality of Gods, Abraham's teachings, eternal glories and the pre-mortal exaltation of some who lived on the earth. "Sons of God who exalt themselves to be Gods, even before the foundation of the world." (TPJS p. 375.) He used as his text the Bible.
Prophets see the meaning behind the words of scripture, and not the words themselves. This is because having been taught by angels and the Lord, they know the intent. Hence Joseph's proclamation that it is his "province to dig up hidden mysteries --new things" using the scriptures. They are not a sealed book to them.
In like manner the Lord spent most of the day of His resurrection opening the scriptures in a private conversation between Himself and two disciples while they walked on the Road to Emmaus. "Beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself." (Luke 24: 27.) The Lord could do this because the Lord was there when they were written, and they reflect His mind and His teachings. Therefore, He could see clearly within them the teachings about Him.
To bear testimony of his encounter with the Lord, and with Moroni, Joseph Smith employed the scriptures to expound unto us in all the scriptures the things concerning himself. How like his Master was this servant! Joseph completely mirrored the pattern of the One who can save! We should be able to recognize the Master in the servant! In Joseph's case, the parallel is unmistakable.
Because he had received a dispensation of the Gospel to him from heaven, Joseph proclaimed the truth using scriptures to confirm the message. "It is the order of heavenly things that God should always send a new dispensation into the world when men have apostatized from the truth and lost the priesthood, but when men come out and build upon other men's foundations, they do it on their own responsibility, without authority from God; and when the floods come and the winds blow, their foundations will be found to be sand, and their whole fabric will crumble to dust." (TPJS p. 375-76.)
Joseph, having secured the truth from heaven for himself, did not need to build on other men's foundations. He was privileged to declare the truth to us from his own understanding, from his own knowledge and in conformity with his own dispensation of the Gospel.
The scriptures weave together the truth from dispensation to dispensation because those who wrote them had seen the same vision, conversed with the same heavenly hosts, and found the inspired language that allows the truth to be declared.
When Joseph wrote his account in 1838, he had pondered and gained the insight to be able to weave into his history the corroboration of his Divine mandate employing the words of scripture to justify what he taught. He was a prophet indeed! He knew the things of which he spoke. All he needed to do was expound the scriptures to be able to dig up hidden mysteries, new things, for those who would hear him. Those who heard him were amazed, just as the disciples on the Road to Emmaus.