Mosiah 21:30

and also that king Noah and his priests had caused the people to commit so many sins and iniquities against God; and they also did mourn for the death of Abinadi; and also for the departure of Alma, and the people that went with him, who had formed a church of God through the strength and power of God, and faith on the words which had been spoken by Abinadi;

They were also sad that King Noah and his priests had made the people sin so much against God. They were sad about the death of Abinadi. They were sad that Alma and the people with him had left. Those people had formed a church of God through God’s strength and power. They had faith in the words Abinadi had spoken.

They also mourned because King Noah and his priests had led the people into so much sin and wickedness against God. They mourned for Abinadi’s death. And they mourned because Alma and his people had left—people who had formed a church of God through his strength and power, and through faith in the words Abinadi had spoken.