The Nephites had been fully converted. They all believed that Christ had been born, according to the sign given of His birth, and that all other prophesy would be fulfilled. They had conquered the Gadianton Robbers, and their faith had caused them to repent and “serve God with all diligence day and night” (v. 3). The Nephites imprisoned the surviving Robbers and preached the gospel to them. Those who repented and covenanted were set free. Those who weren't converted were somehow dealt with, and “thus they did put an end to all those wicked, and secret, and abominable combinations” (v. 6).
How I wish our faith would lead us to serve God diligently and repent in such a fashion that we could “imprison” our sins and shortcomings until we had conquered them or made them strengths, and otherwise dealt with them. Then we could put an end to the sins and weaknesses that cause us so much suffering. How do we imprison our sins? Turning to God goes a long way, for as James wrote, “Resist the devil, and he will flee from you” (James 4:7).