Alma 24:16 - 24:20
Alma 24:16 And now, my brethren, if our brethren seek to destroy us, behold, we will hide away our swords, yea, even we will bury them deep in the earth, that they may be kept bright, as a testimony that we have never used them, at the last day; and if our brethren destroy us, behold, we shall go to our God and shall be saved.
The king proposed and wanted those assembled who were hearing his words to bury their weapons deep in the ground. In this manner they would not be a tempted to take them up again to make war even if their fellow Lamanites attached them. In addition this token would be a sign to God that they were willing to do all that was necessary for them to be saved.
Alma 24:17 And now it came to pass that when the king had made an end of these sayings, and all the people were assembled together, they took their swords, and all the weapons which were used for the shedding of man’s blood, and they did bury them up deep in the earth.
The assembly accepted his proposal and did indeed bury all their weapons of war deep in the earth.
Alma 24:18 And this they did, it being in their view a testimony to God, and also to men, that they never would use weapons again for the shedding of man’s blood; and this they did, vouching and covenanting with God, that rather than shed the blood of their brethren they would give up their own lives; and rather than take away from a brother they would give unto him; and rather than spend their days in idleness they would labor abundantly with their hands.
This act was a symbol to God that they were willing to follow God even if it resulted in their falling victim to attacks by their brethren. Also to show God that they were not anymore going to be thieves and murders to get gain, but that they would work to support themselves and the poor among them.
Alma 24:19 And thus we see that, when these Lamanites were brought to believe and to know the truth, they were firm, and would suffer even unto death rather than commit sin; and thus we see that they buried their weapons of peace, or they buried the weapons of war, for peace.
Mormon editorializes here by telling us that future events will show that these converted Lamanites, when they were brought to learn the truth, that they never lost their testimonies. Now they were willing to suffer death in order to establish peace.
Alma 24:20 And it came to pass that their brethren, the Lamanites, made preparations for war, and came up to the land of Nephi for the purpose of destroying the king, and to place another in his stead, and also of destroying the people of Anti-Nephi-Lehi out of the land.
During this time the Lamanites who were not converted were making preparations for war in order to destroy the Anti-Nephi-Lehis along with their king and replace him with another.