I haven't really noticed this prophecy by Jacob before:
And the time speedily cometh, that except ye repent they [the Lamanites] shall possess the land of your inheritance, and the Lord God will lead away the righteous out from among you. (Jacob 3:4)
We read in 2 Nephi 5, that Nephi and those who wanted to come with him separated from his older brothers and they beame Nephites and Lamanites.
And my people would that we should call the name of the place Nephi; wherefore, we did call it Nephi. (2 Nephi 5:8)
The Nephites lived in the land/city of Nephi for about 350-400 years, until Omni 1:12-13
Behold, I will speak unto you somewhat concerning Mosiah, who was made king over the land of Zarahemla; for behold, he being warned of the Lord that he should flee out of the land of Nephi, and as many as would hearken unto the voice of the Lord should also depart out of the land with him, into the wilderness—
And it came to pass that he did according as the Lord had commanded him. And they departed out of the land into the wilderness, as many as would hearken unto the voice of the Lord; and they were led by many preachings and prophesyings. And they were admonished continually by the word of God; and they were led by the power of his arm, through the wilderness until they came down into the land which is called the land of Zarahemla.
This is the fulfillment of Jacob 3:4. The righteous Nephites fled out of the land of Nephi and Zarahemla now became their new capital. The other part of Jacob's prophecy was that the Lamanites should possess the land of Nephi. Most likely, when the righteous Nephites fled, the remaining wicked Nephites were destroyed by the Lamanites who took their lands in possession. In Mosiah 9, Zeniff is in Zarahemla but is eager to go and live in the land of Nephi
I, Zeniff, having been taught in all the language of the Nephites, and having had a knowledge of the land of Nephi, or of the land of our fathers’ first inheritance
When Zeniff gets there, the land is possessed by Lamanites, demonstrating that this part of Jacob's prophecy also had been fulfilled. Mosiah 9 also talks about the land, "Lehi-Nephi" which I presume to mean the larger area where both the Nephites and Lamanites used to live. That is, when they arrived in the promised land, it was called Lehi. The Lamanites stayed there, while Nephi and his people separated and lived in the land, Nephi.
As usual, this is not straight forward, but internally consistent.
Alma and Amulek preach in the city of Ammonihah, where there is much wickedness. In Alma 9:18, Alma says:
18 But behold, I say unto you that if ye persist in your wickedness that your days shall not be prolonged in the land, for the Lamanites shall be sent upon you; and if ye repent not they shall come in a time when you know not, and ye shall be visited with utter destruction; and it shall be according to the fierce anger of the Lord.
In Alma 10:22-23, Amulek says:
22 Yea, and I say unto you that if it were not for the prayers of the righteous, who are now in the land, that ye would even now be visited with utter destruction; yet it would not be by flood, as were the people in the days of Noah, but it would be by famine, and by pestilence, and the sword.
23 But it is by the prayers of the righteous that ye are spared; now therefore, if ye will cast out the righteous from among you then will not the Lord stay his hand; but in his fierce anger he will come out against you; then ye shall be smitten by famine, and by pestilence, and by the sword; and the time is soon at hand except ye repent.
The people have been warned: If they don't repent, the Lamanites will visit them with utter destruction. It has not happened yet, only because of the prayers of the righteous. But if they cast out the righteous, the Lord will not "stay his hand".
What did the people of Ammonihah do? Alma 14:7:
And they spit upon him, and cast him out from among them, and also all those who believed in the words which had been spoken by Alma and Amulek; and they cast them out, and sent men to cast stones at them.
Alma 15:15
But as to the people that were in the land of Ammonihah, they yet remained a hard-hearted and a stiffnecked people; and they repented not of their sins,
Basically exactly what they were warned against.
What happened next? Alma 16:2-3
2 For behold, the armies of the Lamanites had come in upon the wilderness side, into the borders of the land, even into the city of Ammonihah, and began to slay the people and destroy the city.
3 And now it came to pass, before the Nephites could raise a sufficient army to drive them out of the land, they had destroyed the people who were in the city of Ammonihah
This is a continuation from part 1. Mormon is making sure to record the fulfillment of all of Samuel's prophecies, even the one the Nephites forgot to record at the time (see example 8).
Example 6: Signs of Christ's birth in Helaman 14:4-5,7
4 Therefore, there shall be one day and a night and a day, as if it were one day and there were no night; and this shall be unto you for a sign; for ye shall know of the rising of the sun and also of its setting; therefore they shall know of a surety that there shall be two days and a night; nevertheless the night shall not be darkened; and it shall be the night before he is born.
5 And behold, there shall a new star arise, such an one as ye never have beheld; and this also shall be a sign unto you.
7 And it shall come to pass that ye shall all be amazed, and wonder, insomuch that ye shall fall to the earth.
The fulfillment is described in 3 Nephi 1:15-16,19-21
15 And it came to pass that the words which came unto Nephi were fulfilled, according as they had been spoken; for behold, at the going down of the sun there was no darkness; and the people began to be astonished because there was no darkness when the night came.
16 And there were many, who had not believed the words of the prophets, who fell to the earth and became as if they were dead
19 And it came to pass that there was no darkness in all that night, but it was as light as though it was mid-day. And it came to pass that the sun did rise in the morning again, according to its proper order; and they knew that it was the day that the Lord should be born, because of the sign which had been given.
20 And it had come to pass, yea, all things, every whit, according to the words of the prophets.
21 And it came to pass also that a new star did appear, according to the word.
Notice the subtle consistency between the "night before he is born" and "the day that the Lord should be born".
Example 7: Signs of Christ's death in Helaman 14:20-24
20 But behold, as I said unto you concerning another sign, a sign of his death, behold, in that day that he shall suffer death the sun shall be darkened and refuse to give his light unto you; and also the moon and the stars; and there shall be no light upon the face of this land, even from the time that he shall suffer death, for the space of three days, to the time that he shall rise again from the dead.
21 Yea, at the time that he shall yield up the ghostthere shall be thunderings and lightnings for the space of many hours, and the earth shall shake and tremble; and the rocks which are upon the face of this earth, which are both above the earth and beneath, which ye know at this time are solid, or the more part of it is one solid mass, shall be broken up;
22 Yea, they shall be rent in twain, and shall ever after be found in seams and in cracks, and in broken fragments upon the face of the whole earth, yea, both above the earth and beneath.
23 And behold, there shall be great tempests, and there shall be many mountains laid low, like unto a valley, and there shall be many places which are now called valleys which shall become mountains, whose height is great.
24 And many highways shall be broken up, and many cities shall become desolate.
Compare with 3 Nephi 8:12-13, 19-23
12 But behold, there was a more great and terrible destruction in the land northward; for behold, the whole face of the land was changed, because of the tempest and the whirlwinds, and the thunderings and the lightnings, and the exceedingly great quaking of the whole earth;
13 And the highways were broken up, and the level roads were spoiled, and many smooth places became rough.
18 And behold, the rocks were rent in twain; they were broken up upon the face of the whole earth, insomuch that they were found in broken fragments, and in seams and in cracks, upon all the face of the land.
19 And it came to pass that when the thunderings, and the lightnings, and the storm, and the tempest, and the quakings of the earth did cease—for behold, they did last for about the space of threehours; and it was said by some that the time was greater; nevertheless, all these great and terrible things were done in about the space of three hours—and then behold, there was darkness upon the face of the land.
20 And it came to pass that there was thick darkness upon all the face of the land, insomuch that the inhabitants thereof who had not fallen could feel the vapor of darkness;
21 And there could be no light, because of the darkness, neither candles, neither torches; neither could there be fire kindled with their fine and exceedingly dry wood, so that there could not be any light at all;
22 And there was not any light seen, neither fire, nor glimmer, neither the sun, nor the moon, nor the stars, for so great were the mists of darkness which were upon the face of the land.
23 And it came to pass that it did last for the space of three days that there was no light seen
Check the two compared texts marked with green again. Do you see all the repeated expressions? "Rent in twain", "broken up", "broken fragments", "seams and in cracks"... To me, there is only one reasonable explanation; that the author of 3 Nephi 8 had (notes from) the text from Helaman 14 in front of him.
Example 8: The forgotten prophecy about the resurrected saints in Helaman 14:25
And many graves shall be opened, and shall yield up many of their dead; and many saints shall appear unto many.
This one is not recorded in 3 Nephi 8. I'm not blaming Mormon, who abridged the Nephite record. He actually made sure to include Christ's words when He later asks the Nephite record keepers why it had not been included. 3 Nephi 23:7-13
7 And it came to pass that he said unto Nephi: Bring forth the record which ye have kept.
8 And when Nephi had brought forth the records, and laid them before him, he cast his eyes upon them and said:
9 Verily I say unto you, I commanded my servant Samuel, the Lamanite, that he should testify unto this people, that at the day that the Father should glorify his name in me that there were manysaints who should arise from the dead, and should appear unto many, and should minister unto them. And he said unto them: Was it not so?
10 And his disciples answered him and said: Yea, Lord, Samuel did prophesy according to thy words, and they were all fulfilled.
11 And Jesus said unto them: How be it that ye have not written this thing, that many saints did arise and appear unto many and did minister unto them?
12 And it came to pass that Nephi remembered that this thing had not been written.
13 And it came to pass that Jesus commanded that it should be written; therefore it was written according as he commanded
The Nephite record keepers included this addition later when Jesus commanded them to write it and Mormon included it by relating this incident.
Conclusion
Samuel's prophecies are numerous and very specific and so is the description of their fulfillment. This is one of several examples where Mormon goes out of his way to demonstrate that prophecies have been fulfilled. It also gives 8 examples (and I might have overlooked some) of internal consistency in the Book of Mormon, some examples actually containing multiple connected phrases. We have seen numerous others before on this blog. With the risk of repeating myself too much, this carefully crafted text can only be dictated in one draft with your face in a hat if you have divine help.