Look to Abraham (v 1-3)
The Lord reminds and comforts Israel as he commands them to "look unto the rock whence ye are hewn" and to "look unto Abraham your father" (Isaiah 51:1-2). As a continuation from the previous chapter, the Lord is trying to comfort Israel by telling her to trust in Him. He provides more evidence to Israel by showing her how He has blessed Abraham and his posterity. Abraham was a single man. Now his posterity are nations.
The covenants the Lord made with Abraham were in effect during Isaiah's time and are still in effect today. They were fulfilled and being fulfilled in Isaiah's time and they are fulfilled and still being fulfilled today.
Being heirs and descendants of Abraham, we too can receive the same blessings Abraham was promised if we keep the covenants we've made with the Lord.
Elder Nelson summarizes the blessings we will receive as we keep our covenants.
"Abraham’s posterity would be numerous, entitled to eternal increase and to bear the priesthood;
• He would become a father of many nations;
• Christ and kings would come through Abraham’s lineage;
• Certain lands would be inherited;
• All nations of the earth would be blessed by his seed;
• That covenant would be everlasting—even through “a thousand generations.”"
(Russell M. Nelson, “Children of the Covenant,” Ensign, May 1995, 32)
He references the following scriptures in his talk:
Gen. 17:1–10; Gen. 22:15–18; Gal. 3:28–29; Abr. 2:9–11.
Gen. 26:1–5, 24.
Gen. 28:1–4, 10–14; Gen. 35:9–13; Gen. 48:3–4.
1 Chr. 16:15. See also Gen. 17:1–10, 19; Lev. 26:42; Acts 3:25; LDS Bible Dictionary, “Abraham, Covenant of,” p. 602.
The Work and Glory (v 4-8)
The Lord further comforts Israel by telling her His work will last forever. In Isaiah 51:6 he says "the heavens shall vanish away like smoke, and the earth shall wax old like a garment, and they that dwell therein shall die in like manner: but my salvation shall be for ever, and my righteousness shall not be abolished."
Like Joseph Smith has declared, the Lord's work cannot be stopped. My parents sent me a quote from Joseph Smith while they and I were on missions. They said they repeated this quote every conference and were asked to memorize it.
In the Wentworth Letter, Joseph Smith wrote, "Our missionaries are going forth to different nations, and in Germany, Palestine, New Holland, Australia, the East Indies, and other places, the Standard of Truth has been erected; no unhallowed hand can stop the work from progressing; persecutions may rage, mobs may combine, armies may assemble, calumny may defame, but the truth of God will go forth boldly, nobly, and independent, till it has penetrated every continent, visited every clime, swept every country, and sounded in every ear; till the purposes of God shall be accomplished, and the Great Jehovah shall say the work is done." (see Joseph Smith Jr., “The Wentworth Letter,” Ensign, Jul 2002, 27)
Our Protector, Our Comforter (v 9-16)
The Lord reminds Israel that he has comforted and protected them. He has done so in the past and he will continue to do so in the future. If ever we feel fear or doubt, reading Isaiah 51:12-16 will bring us comfort.
Two Sons to Lead (v 17-23)
The Book of Mormon version of Isaiah 51 sheds some vital information that is left out in the Old Testament version. I've marked the key difference between the two sources.
Isaiah 51:19-20 says, "These two things are come unto thee; who shall be sorry for thee? Desolation, and destruction, and the famine, and the sword: by whom shall I comfort thee?
"Thy sons have fainted, they lie at the head of all the streets, as a wild bull in a net: they are full of the fury of the Lord, the rebuke of they God."
2 Nephi 8:19-20 reads, "These two sons are come unto thee, who shall be sorry for thee—thy desolation and destruction, and the famine and the sword—and by whom shall I comfort thee?
"Thy sons have fainted, save these two; they lie at the head of all the streets; as a wild bull in a net, they are full of the fury of the Lord, the rebuke of thy God."
Ludlow notes that in Revelation 11:1-6, "John the Revelator describes two great servants of God who will stand and fight for Jerusalem against the armies of the world. For three and one-half years they will have power over the heavens, earth, and their enemies. Then they will killed." (431) The entire chapter of Revelation 11 is a great source for more information on these two prophets.
Joseph Smith also spoke of these two great prophets in D&C 77:15 teaching us that they will be "raised up to the Jewish nation in the last days, at the time of the restoration, and to prophesy to the Jews after they are gathered and have built the city of Jerusalem in the land of their fathers."
This article (Brent Bulloch, “I Have a Question,” Ensign, Dec. 1981, 58–60) notes that "Two prophets will be raised up unto (not from) the Jewish nation after the gathering." They key point being that they will not be Jewish.
In another article (Daniel H. Ludlow, “The Future of the Holy Land,” Ensign, May 1972, 96) the author quotes Orson Pratt, “We might bring up, also, the declaration of John in relation to the two witnesses who are to prophecy about that period. They are to prophecy three and a half years, and their field of labor will be Jerusalem, after it shall have been rebuilt by the Jews. By means of their prophecies and the power of God attending them, the nations who are gathered together against Jerusalem will be kept at bay, these Prophets will hold them in check by their faith and power. By and by these nations overcome the two witnesses and, having finished their mission, they are slain, and their bodies will lie three days and a half in the streets of the city. Then a great earthquake will take place, and these two witnesses will be caught up to heaven.” (JD, vol. 16, p. 329. Italics added.)"
Bruce R. McConkie has also commented on these two great prophets. "These two shall be followers of that humble man, Joseph Smith, through whom the Lord of Heaven restored the fullness of his everlasting gospel in this final dispensation of grace. No doubt they will be members of the Council of the Twelve or of the First Presidency of the Church. Their prophetic ministry to rebellious Jewry shall be the same in length as was our Lord's personal ministry among their rebellious forebears." (McConkie, Bruce R. Doctrinal New Testament Commentary. 3:507-511. Salt Lake City: Bookcraft, 1965-73)
On a personal note … I have always been fascinated with this prophecy. As a kid, I imagined that the whole world will see these two prophets' bodies lying in the streets dead. I can almost hear the commentary of the newscasters and the world rejoicing that they are dead. Then they will be resurrected and fear will grip the world … much like the fear that gripped the people of Ammonihah when they saw Alma and Amulek stepping out of the ruins of the prison in which they were held. The people fled before those two prophets "as a goat fleeth with her young from two lions" (Alma 14:29)
I don't know when all this will happen, but deep down inside, I feel strongly that it will happen in my lifetime.