It is important to note that part of the preparation for the coming of Christ to the Americas was to soften their hearts so that they could accept the teachings that Christ brought with him.
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We have not yet received all the information that the Lord taught the Nephites at his coming. Some of the information he taught they were not allowed to utter or make known. However, we do know that it was information that would allow them to be grafted into the true vine and to enter into the rest of the Lord.
Mormon intended to include all that the Lord taught the Nephites in the Book of Mormon, however he did not, he explains what happened,
3 Ne 26:6-11
6 And now there cannot be written in this book even a hundredth part of the things which Jesus did truly teach unto the people;
7 But behold the plates of Nephi do contain the more part of the things which he taught the people.
8 And these things have I written, which are a lesser part of the things which he taught the people; and I have written them to the intent that they may be brought again unto this people, from the Gentiles, according to the words which Jesus hath spoken.
9 And when they shall have received this, which is expedient that they should have first, to try their faith, and if it shall so be that they shall believe these things then shall the greater things be made manifest unto them.
10 And if it so be that they will not believe these things, then shall the greater things be withheld from them, unto their condemnation.
11 Behold, I was about to write them, all which were engraven upon the plates of Nephi, but the Lord forbade it, saying: I will try the faith of my people.
When the Lord did visit the Nephites the people were believing and loved to bask in his presence. However, there minds were weak and they could not understand the things that he taught them,
3 Ne 17:1-3
1 Behold, now it came to pass that when Jesus had spoken these words he looked round about again on the multitude, and he said unto them: Behold, my time is at hand.
2 I perceive that ye are weak, that ye cannot understand all my words which I am commanded of the Father to speak unto you at this time.
3 Therefore, go ye unto your homes, and ponder upon the things which I have said, and ask of the Father, in my name, that ye may understand, and prepare your minds for the morrow, and I come unto you again.
As we can see, He actually gave them homework so that they would be prepared for the next day when the twelve, that he has chosen, repeated everything word for word. He then came and continued on from the exact place that he had left off from the day before.
What can be learned from this experience? The Father had commanded the Savior to teach specific things to the Nephites, therefore, the Savior was determined that he would teach them and that they needed to prepare their minds by focusing on his doctrine and praying about the meaning of the things taught.
From 3 Nephi 26:10-11 we learn that our faith is being tested to see how seriously we take the commandments and doctrine learned in our Book of Mormon. We need the information that the Savior taught to the Nephite so that we can avoid condemnation.
We must read, study, ponder, and pray about the things that the Lord has revealed to us thus far in all of the scriptures, so that when he comes our minds are not weak and we can understand his teachings.
We learn from the revelations that when the Lord comes his is going to reveal information that will finish the process of turning our earth into a Celestial Kingdom and the inhabitants into Gods. The two scripture quotes that follow help us to see the wealth of knowledge that the Lord will bring with him,
26 God shall give unto you knowledge by his holy Spirit, yea, by the unspeakable gift of the Holy Ghost, that has not been revealed since the world was until now;
27 Which our forefathers have awaited with anxious expectation to be revealed in the last times, which their minds were pointed to by the angels, as held in reserve for the fulness of their glory;
28 A time to come in the which nothing shall be withheld, whether there be one God or many gods, they shall be manifest.
29 All thrones and dominions, principalities and powers, shall be revealed and set forth upon all who have endured valiantly for the gospel of Jesus Christ.
30 And also, if there be bounds set to the heavens or to the seas, or to the dry land, or to the sun, moon, or stars--
31 All the times of their revolutions; all the appointed days, months, and years, and all the days of their days, months, and years, and all their glories, laws, and set times, shall be revealed in the days of the dispensation of the fulness of times--
32 According to that which was ordained in the midst of the Council of the Eternal God of all other gods before this world was, that should be reserved unto the finishing and the end thereof, when every man shall enter into his eternal presence and into his immortal rest.
32 Yea, verily I say unto you, in that day when the Lord shall come, he shall reveal all things--
33 Things which have passed, and hidden things which no man knew, things of the earth, by which it was made, and the purpose and the end thereof--
34 Things most precious, things that are above, and things that are beneath, things that are in the earth, and upon the earth, and in heaven.
35 And all they who suffer persecution for my name, and endure in faith, though they are called to lay down their lives for my sake yet shall they partake of all this glory.
36 Wherefore, fear not even unto death; for in this world your joy is not full, but in me your joy is full.
37 Therefore, care not for the body, neither the life of the body; but care for the soul, and for the life of the soul.
From this we can see that those who are exalted after the earth is Celestialized truly will know all things. The Lord has reseved the phase of this earthly probation to teach the righteous all things, nothing being withheld. There is a direct relationship between our obedience and righteousness and an inquiring mind and what we learn and know. No wonder in the sermon on the mount the Savior commanded us to ask. He promised that everyone who asked would receive. He further commaned us to seek and to knock and that we would find and have things opened unto us (Matt. 7:7-8).