Alma 24:18

and this they did, it being in their view a testimony to God, and also to men, that they never use weapons again for the shedding of man’s blood; and this they did, vouching and covenanting with God, that rather than to shed the blood of their brethren, they would give up their own lives; and rather than to take away from a brother, they would give unto him; and rather than to spend their days in idleness, they would labor abundantly with theit hands;

They did this as proof to God and to people that they would never use weapons again to kill anyone. They did this, making a promise with God. They would rather give up their own lives than kill their brothers. They would rather give to a brother than take from him. They would rather work hard with their hands than spend their days doing nothing.

This was their testimony to God and to everyone that they would never again use weapons to take human life. They made a sacred promise to God: they would rather die than kill their brothers. They would rather give to someone than take from them. They would rather work hard than waste their days in laziness.