And many graves shall be opened, and shall yield up many of their dead; and many saints shall appear unto many. Helaman 14:25 14:25
Samuel continued his sermon on the wall. He said many more things that Helaman couldn't put in his plates.
But here is more of what Samuel said:
The Son of God will come in five years. 
3 And behold, this will I give unto you for a sign at the time of his coming; for behold, there shall be great lights in heaven, insomuch that in the night before he cometh there shall be no darkness, insomuch that it shall appear unto man as if it was day.
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.
The night before Jesus is born there will great lights in the sky that will make the night as bright as day! 
When Jesus is born, a new star will arise that no one had ever seen before, along with many other astronomical signs and wonders.
When you see these things, you'lll fall to earth. 
9 And behold, thus hath the Lord commanded me, by his angel, that I should come and tell this thing unto you; yea, he hath commanded that I should prophesy these things unto you; yea, he hath said unto me: Cry unto this people, repent and prepare the way of the Lord.
10 And now, because I am a Lamanite, and have spoken unto you the words which the Lord hath commanded me, and because it was hard against you, ye are angry with me and do seek to destroy me, and have cast me out from among you.
11 And ye shall hear my words, for, for this intent have I come up upon the walls of this city, that ye might hear and know of the judgments of God which do await you because of your iniquities, and also that ye might know the conditions of repentance;
God commanded me by his angel to tell you this.
12 And also that ye might know of the coming of Jesus Christ, the Son of God, the Father of heaven and of earth, the Creator of all things from the beginning; and that ye might know of the signs of his coming, to the intent that ye might believe on his name.
He also told me to tell you that Jesus Christ is the Son of God, the Father of heaven and earth, and the Creator of all things. 
15 For behold, he surely must die that salvation may come; yea, it behooveth him and becometh expedient that he dieth, to bring to pass the resurrection of the dead, that thereby men may be brought into the presence of the Lord.
16 Yea, behold, this death bringeth to pass the resurrection, and redeemeth all mankind from the first death -- that spiritual death; for all mankind, by the fall of Adam being cut off from the presence of the Lord, are considered as dead, both as to things temporal and to things spiritual.
If you repent and believe on his name you might be forgiven for your sins. 
18 Yea, and it bringeth to pass the condition of repentance, that whosoever repenteth the same is not hewn down and cast into the fire; but whosoever repenteth not is hewn down and cast into the fire; and there cometh upon them again a spiritual death, yea, a second death, for they are cut off again as to things pertaining to righteousness.
Otherwise you'll be cast into the fire of hell.
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.
When Jesus dies it will be absolutely dark for three days and nights. No sun, moon, or stars will be seen anywhere on earth for 72 hours. 
21 Yea, at the time that he shall yield up the ghost there 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;
But that's not all that will happen after Jesus dies.
There will be thunder and lightning for many hours, the earth will shake, and rocks will break.
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.
There will be great storms, many mountains will be smashed into valleys, valleys will become mountains,
highways will break apart, cities will be destroyed,
dead people will walk around,
27 And he said unto me that while the thunder and the lightning lasted, and the tempest, that these things should be, and that darkness should cover the face of the whole earth for the space of three days.
and there will be complete darkness over the entire earth for three days.
28 And the angel said unto me that many shall see greater things than these, to the intent that they might believe that these signs and these wonders should come to pass upon all the face of this land, to the intent that there should be no cause for unbelief among the children of men --
All these things will happen so that everyone on earth will see the signs, so there'll be no excuse for unbelief.
29 And this to the intent that whosoever will believe might be saved, and that whosoever will not believe, a righteous judgment might come upon them; and also if they are condemned they bring upon themselves their own condemnation.
30 And now remember, remember, my brethren, that whosoever perisheth, perisheth unto himself; and whosoever doeth iniquity, doeth it unto himself; for behold, ye are free; ye are permitted to act for yourselves; for behold, God hath given unto you a knowledge and he hath made you free.
31 He hath given unto you that ye might know good from evil, and he hath given unto you that ye might choose life or death; and ye can do good and be restored unto that which is good, or have that which is good restored unto you; or ye can do evil, and have that which is evil restored unto you.
God has made you free, so use your freedom wisely.
Believe and be saved; disbelieve and be damned.
It's your choice.