It is a gross understatement to describe the Prophet Joseph Smith’s mind as “bright and enlightened,” but it’s a good starting point for understanding the man who became the conduit of the revelations contained in the Doctrine and Covenants.
Most scriptures present us with the word of the Lord and invitations to repent filtered through the voices and perspectives of various prophets, apostles, and other men of God. D&C 19 (along with most of the Doctrine and Covenants) is unique because although the Prophet Joseph Smith was the conduit of the message, the Lord Himself speaks in the first person directly to His audience.
When Martin Harris repeatedly badgered the Prophet Joseph Smith and petitioned the Lord for “a commandment,” he probably wasn’t expecting the commandment that he received in D&C 19. Martin Harris was probably seeking for reassurance about Book of Mormon sales, his family, and his farm. Instead, he received as stern a rebuke and as powerful an admonition as can be found anywhere in scripture:
And surely every man must repent or suffer, for I, God, am endless.
Wherefore, I revoke not the judgments which I shall pass, but woes shall go forth, weeping, wailing and gnashing of teeth, yea, to those who are found on my left hand.
Nevertheless, it is not written that there shall be no end to this torment, but it is written endless torment.
Again, it is written eternal damnation; wherefore it is more express than other scriptures, that it might work upon the hearts of the children of men, altogether for my name’s glory.
Wherefore, I will explain unto you this mystery, for it is meet unto you to know even as mine apostles.
I speak unto you that are chosen in this thing, even as one, that you may enter into my rest.
For, behold, the mystery of godliness, how great is it! For, behold, I am endless, and the punishment which is given from my hand is endless punishment, for Endless is my name. Wherefore—
Eternal punishment is God’s punishment.
Endless punishment is God’s punishment.
Wherefore, I command you to repent, and keep the commandments which you have received by the hand of my servant Joseph Smith, Jun., in my name;
And it is by my almighty power that you have received them; (D&C 19:4-14)
These are great passages to ponder and apply during Lent which began with Ash Wednesday yesterday.
There is no ambiguity whatsoever in the Lord’s commandment to each one of us to repent. In this revelation to Martin Harris, we also gain additional insights into why the Lord commanded Martin Harris and each one of us to repent. The commandment to repent is merciful because the Lord does not want us to suffer. The Lord does not want us to experience His punishment (Endless and Eternal punishment), but to repent, to understand the mystery of godliness, and to enter into His rest.

Therefore I command you to repent—repent, lest I smite you by the rod of my mouth, and by my wrath, and by my anger, and your sufferings be sore—how sore you know not, how exquisite you know not, yea, how hard to bear you know not.
For behold, I, God, have suffered these things for all, that they might not suffer if they would repent;
But if they would not repent they must suffer even as I;
Which suffering caused myself, even God, the greatest of all, to tremble because of pain, and to bleed at every pore, and to suffer both body and spirit—and would that I might not drink the bitter cup, and shrink—
Nevertheless, glory be to the Father, and I partook and finished my preparations unto the children of men.
Wherefore, I command you again to repent, lest I humble you with my almighty power; and that you confess your sins, lest you suffer these punishments of which I have spoken, of which in the smallest, yea, even in the least degree you have tasted at the time I withdrew my Spirit. (D&C 19:15-20)
Most of what we learn in the scriptures about the unfathomable and incomprehensible agony that Jesus Christ suffered in Gethsemane and on the Cross of Calvary has been transmitted to us by others who witnessed the events from the outside. For example, King Benjamin taught his people about Jesus Christ’s suffering as follows:
And lo, he shall suffer temptations, and pain of body, hunger, thirst, and fatigue, even more than man can suffer, except it be unto death; for behold, blood cometh from every pore, so great shall be his anguish for the wickedness and the abominations of his people. (Mosiah 3:7)
Alma described our Savior’s suffering as follows:
And he shall go forth, suffering pains and afflictions and temptations of every kind; and this that the word might be fulfilled which saith he will take upon him the pains and the sicknesses of his people.
And he will take upon him death, that he may loose the bands of death which bind his people; and he will take upon him their infirmities, that his bowels may be filled with mercy, according to the flesh, that he may know according to the flesh how to succor his people according to their infirmities. (Alma 7:11-12)
In His revelation to Martin Harris, however, Jesus Christ described His suffering from His own perspective.
To describe His own suffering to Martin Harris and to us, our beloved Savior used words such as sore, exquisite, hard to bear, tremble, pain, bleed at every pour, suffer both body and spirit, and bitter cup. His suffering was more sore, exquisite, and hard to bear than Martin Harris or any one of us can comprehend, but Jesus Christ gives us a glimpse of what He suffered in order to persuade us to repent.
Why was Jesus Christ willing to suffer?
One of our Savior’s final teachings to His disciples before His suffering in Gethsemane and the Cross of Calvary helps us to answer this question:
Greater love hath no man than this, that a man lay down his life for his friends. (John 15:13)
What caused God, the greatest of all, suffering so sore, exquisite, and hard to bear? What caused God, the greatest of all, to tremble because of pain, to bleed at every pore, and to suffer both body and spirit? What caused God, the greatest of all, to wish not to drink the bitter cup?
As I study these passages, it seems to me that our Savior had much more to say about His suffering, but for Martin Harris’ sake, and for our sake, He abbreviated His account in order to glorify the Father and to testify that He had finished His preparations unto the children of men. It may be that our Savior also abbreviated His account of His suffering because He knew that no mortal man, including Martin Harris, could ever truly understand what He endured.