The sons of Mosiah show how to gain spiritual strength

From the experience of the sons of Mosiah we can learn how to gain
spiritual strength. In Alma 17, Alma reunites with the sons of Mosiah
who had for 14 years served among the Lamanites. They had gained
spiritual strength because they had searched the scriptures
diligently, that they might know the word of God. They prayed and
fasted and so had the "spirit of prophecy" and "revelation." The
result was they had "the knowledge of the truth" and "sound
understanding" and "when they taught, they taught with power and
authority of God."

Read more at http://scriptures.lds.org/en/alma/17