Because they had become so wicked, the Lord withdrew His support of the Nephites and left them to fight in their own strength. Even so, in verse 23 He explained that they could receive His strength again if they would repent of their sins and hearken unto His words. To hearken to the Lord’s words indicates more than merely hearing the Lord speak to us through scripture, the still, small voice, etc. To hearken indicates following the Lord’s suggestions. The promise to the reader here appears to be that if we will hearken to the words of the Lord, He will give us the strength to obey them.