Alma 49:30

"Yea, and there was continual peace among them, and exceedingly great prosperity in the church because of their heed and diligence which they gave unto the word of God..."

In this chapter Amalickiah's armies came against two Nephite cities and were astonished at how prepared the Nephites were.  Moroni fortified all the cities, making it possible for them to defend themselves against the numerous enemy armies.  After defeating the Lamanites, the Nephites were grateful for their rescue and devoted their lives to God.  Because they were so devoted to the gospel and truly lived it they had peace and prosperity.  When all church members are heeding the word of God, peace follows.