Mosiah 24 – 25
It sounds like the brethren of Amulon taught the Lamanites the same things they had taught the people under king Noah – except the the people under Noah already knew the language of the Nephites and probably how to read and write. This teaching of the Nephite language doubtlessly paved the way for the missions of the sons of Mosiah.
The Lamanite guards slept through the night while the people of Alma labored and then they slept through the morning while the people of Alma escaped onto their journey wherein they would come to live with a people who had their same faith.