4 Nephi 1:23

And now I, Mormon, would that ye should know that the people had multiplied, insomuch that they were spread upon all the face of the land, and that they had become exceeding rich, because of their prosperity in Christ.

I, Mormon, want you to know that the people had many children. They spread across the whole land. They had become very rich because they did well in Christ.

Now I, Mormon, want you to understand what happened next. The population had grown enormously, spreading across the entire land. They’d become incredibly wealthy because of how well they’d done in Christ.