Alma 46:21 - 46:25
Alma 46: 21 And it came to pass that when Moroni had proclaimed these words, behold, the people came running together with their armor girded about their loins, rending their garments in token, or as a covenant, that they would not forsake the Lord their God; or, in other words, if they should transgress the commandments of God, or fall into transgression, and be ashamed to take upon them the name of Christ, the Lord should rend them even as they had rent their garments.
To give their support to Moroni, all those who heard his message and saw his banner, also put on their body armor and ripped their coats to say they would support Moroni. These steps were also to show the world that if they should ever be ashamed to take upon themselves the name of Christ, them they should be rent like they did their coats.
Alma 46: 22 Now this was the covenant which they made, and they cast their garments at the feet of Moroni, saying: We covenant with our God, that we shall be destroyed, even as our brethren in the land northward, if we shall fall into transgression; yea, he may cast us at the feet of our enemies, even as we have cast our garments at thy feet to be trodden under foot, if we shall fall into transgression.
They then threw their torn coats at the feet of Moroni and made a covenant with God to defend their freedoms and if they should brake the covenant, they should find themselves destroyed at the feet of their enemies just like the torn coats at the feet of Moroni.
Alma 46: 23 Moroni said unto them: Behold, we are a remnant of the seed of Jacob; yea, we are a remnant of the seed of Joseph, whose coat was rent by his brethren into many pieces; yea, and now behold, let us remember to keep the commandments of God, or our garments shall be rent by our brethren, and we be cast into prison, or be sold, or be slain.
Moroni reminded the people that they were descendants of Jacob and therefore of Joseph. It was Joseph’s coat that was ripped up by his brothers. Moroni then compared the torn coat of Joseph to the Nephites. If they should brake the covenant they were now making with God that they suffer the same fate as Joseph’s coat and be ripped up their brethren the Lamanites.
Alma 46: 24 Yea, let us preserve our liberty as a remnant of Joseph; yea, let us remember the words of Jacob, before his death, for behold, he saw that a part of the remnant of the coat of Joseph was preserved and had not decayed. And he said—Even as this remnant of garment of my son hath been preserved, so shall a remnant of the seed of my son be preserved by the hand of God, and be taken unto himself, while the remainder of the seed of Joseph shall perish, even as the remnant of his garment.
Moroni reminds the people of the words of Jacob that he uttered just before his death. Even though he knew most of his descendants would be destroyed by their enemies like most of Joseph’s coat, some of them would be preserved like a part of Joseph’s coat was by God and later enter His kingdom.
Alma 46: 25 Now behold, this giveth my soul sorrow; nevertheless, my soul hath joy in my son, because of that part of his seed which shall be taken unto God.
This was very disheartening for Jacob to know the fate of the majority of his descendants, but he did take sholas in knowing a part would be a righteous people and be able to enter God’s kingdom.