Why it would have been important for Joseph to know about Moses and Joseph Smith so many centuries in advance?
"24 And Joseph said unto his brethren, I die: and God will surely visit you, and bring you out of this land unto the land which he sware to Abraham, to Isaac, and to Jacob.
25 And Joseph took an oath of the children of Israel, saying, God will surely visit you, and ye shall carry up my bones from hence." (Genesis 50:24–25)
"24 And Joseph said unto his brethren, I die, and go unto my fathers; and I go down to my grave with joy. The God of my father Jacob be with you, to deliver you out of affliction in the days of your bondage; for the Lord hath visited me, and I have obtained a promise of the Lord, that out of the fruit of my loins, the Lord God will raise up a righteous branch out of my loins; and unto thee, whom my father Jacob hath named Israel, a prophet; (not the Messiah who is called Shilo;) and this prophet shall deliver my people out of Egypt in the days of thy bondage.
25 And it shall come to pass that they shall be scattered again; and a branch shall be broken off, and shall be carried into a far country; nevertheless they shall be remembered in the covenants of the Lord, when the Messiah cometh; for he shall be made manifest unto them in the latter days, in the Spirit of power; and shall bring them out of darkness into light; out of hidden darkness, and out of captivity unto freedom.
26 A seer shall the Lord my God raise up, who shall be a choice seer unto the fruit of my loins.
27 Thus saith the Lord God of my fathers unto me, A choice seer will I raise up out of the fruit of thy loins, and he shall be esteemed highly among the fruit of thy loins; and unto him will I give commandment that he shall do a work for the fruit of thy loins, his brethren.
28 And he shall bring them to the knowledge of the covenants which I have made with thy fathers; and he shall do whatsoever work I shall command him.
29 And I will make him great in mine eyes, for he shall do my work; and he shall be great like unto him whom I have said I would raise up unto you, to deliver my people, O house of Israel, out of the land of Egypt; for a seer will I raise up to deliver my people out of the land of Egypt; and he shall be called Moses. And by this name he shall know that he is of thy house; for he shall be nursed by the king’s daughter, and shall be called her son.
30 And again, a seer will I raise up out of the fruit of thy loins, and unto him will I give power to bring forth my word unto the seed of thy loins; and not to the bringing forth of my word only, saith the Lord, but to the convincing them of my word, which shall have already gone forth among them in the last days;
31 Wherefore the fruit of thy loins shall write, and the fruit of the loins of Judah shall write; and that which shall be written by the fruit of thy loins, and also that which shall be written by the fruit of the loins of Judah, shall grow together unto the confounding of false doctrines, and laying down of contentions, and establishing peace among the fruit of thy loins, and bringing them to a knowledge of their fathers in the latter days; and also to the knowledge of my covenants, saith the Lord.
32 And out of weakness shall he be made strong, in that day when my work shall go forth among all my people, which shall restore them, who are of the house of Israel, in the last days.
33 And that seer will I bless, and they that seek to destroy him shall be confounded; for this promise I give unto you; for I will remember you from generation to generation; and his name shall be called Joseph, and it shall be after the name of his father; and he shall be like unto you; for the thing which the Lord shall bring forth by his hand shall bring my people unto salvation.
34 And the Lord sware unto Joseph that he would preserve his seed forever, saying, I will raise up Moses, and a rod shall be in his hand, and he shall gather together my people, and he shall lead them as a flock, and he shall smite the waters of the Red Sea with his rod.
35 And he shall have judgment, and shall write the word of the Lord. And he shall not speak many words, for I will write unto him my law by the finger of mine own hand. And I will make a spokesman for him, and his name shall be called Aaron.
36 And it shall be done unto thee in the last days also, even as I have sworn. Therefore, Joseph said unto his brethren, God will surely visit you, and bring you out of this land, unto the land which he sware unto Abraham, and unto Isaac, and to Jacob.
37 And Joseph confirmed many other things unto his brethren, and took an oath of the children of Israel, saying unto them, God will surely visit you, and ye shall carry up my bones from hence.
38 So Joseph died when he was an hundred and ten years old; and they embalmed him, and they put him in a coffin in Egypt; and he was kept from burial by the children of Israel, that he might be carried up and laid in the sepulchre with his father. And thus they remembered the oath which they sware unto him." (Joseph Smith Translation, Genesis 50:24–38)
"17 Wherefore, I the Lord, knowing the calamity which should come upon the inhabitants of the earth, called upon my servant Joseph Smith, Jun., and spake unto him from heaven, and gave him commandments;
18 And also gave commandments to others, that they should proclaim these things unto the world; and all this that it might be fulfilled, which was written by the prophets—
19 The weak things of the world shall come forth and break down the mighty and strong ones, that man should not counsel his fellow man, neither trust in the arm of flesh—
20 But that every man might speak in the name of God the Lord, even the Savior of the world;
21 That faith also might increase in the earth;
22 That mine everlasting covenant might be established;
23 That the fulness of my gospel might be proclaimed by the weak and the simple unto the ends of the world, and before kings and rulers." (Doctrine and Covenants 1:17–23)
"7 And gave unto him commandments which inspired him;
8 And gave him power from on high, by the means which were before prepared, to translate the Book of Mormon;
9 Which contains a record of a fallen people, and the fulness of the gospel of Jesus Christ to the Gentiles and to the Jews also;
10 Which was given by inspiration, and is confirmed to others by the ministering of angels, and is declared unto the world by them—
11 Proving to the world that the holy scriptures are true, and that God does inspire men and call them to his holy work in this age and generation, as well as in generations of old;
12 Thereby showing that he is the same God yesterday, today, and forever. Amen." (Doctrine and Covenants 20:7–12)
"11 And if thou do this, I have prepared thee for a greater work. Thou shalt preach the fulness of my gospel, which I have sent forth in these last days, the covenant which I have sent forth to recover my people, which are of the house of Israel." (Doctrine and Covenants 39:11)
"3 Joseph Smith, the Prophet and Seer of the Lord, has done more, save Jesus only, for the salvation of men in this world, than any other man that ever lived in it. In the short space of twenty years, he has brought forth the Book of Mormon, which he translated by the gift and power of God, and has been the means of publishing it on two continents; has sent the fulness of the everlasting gospel, which it contained, to the four quarters of the earth; has brought forth the revelations and commandments which compose this book of Doctrine and Covenants, and many other wise documents and instructions for the benefit of the children of men; gathered many thousands of the Latter-day Saints, founded a great city, and left a fame and name that cannot be slain. He lived great, and he died great in the eyes of God and his people; and like most of the Lord’s anointed in ancient times, has sealed his mission and his works with his own blood; and so has his brother Hyrum. In life they were not divided, and in death they were not separated!" (Doctrine and Covenants 135:3)
And here's the commentary entitled: “A seer shall the Lord my God raise up.” :
"As you read Genesis 50:24–25 and Joseph Smith Translation, Genesis 50:24–38 (in the Bible appendix), ponder why it would have been important for Joseph to know about Moses and Joseph Smith so many centuries in advance. How did Joseph Smith fulfill Joseph’s prophecies about him? (see Doctrine and Covenants 1:17–23; 20:7–12; 39:11; 135:3)."
It would have been important for Joseph to know about Moses and Joseph Smith so many centuries in advance because it would have given him the assurance that the Lord's promises are true and will all be fulfilled. Joseph Smith fulfilled Joseph's prophecies about him by translating the Book of Mormon and bringing the descendants of Joseph (the children of Lehi) to the knowledge of the covenants which their fathers made with God.
