These comparisons follow the form of the model text in 3 Nephi:
Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.
A good tree cannot bring forth evil fruit, neither a corrupt tree bring forth good fruit.
Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
Wherefore, by their fruits ye shall know them. (3 Ne. 14:16–20.)
However, Mormon doesn’t repeat the example but expands on the form with his own examples. He is faithful to the literary phrasing but invents the specifics of the images. Mormon’s message is that one should “endure to the end.”