Lehi is confirming that the Lord has shown him the destruction of Jerusalem and telling us of the setting apart of the promised land for a righteous people. This is a broad scale prophesy, but what does it mean to qualify for the promised land at an individual level and how does individual actions disqualify a people for the promised land?
Lehi gives blessings to his eldest sons. Why does iniquity destroy not only yourself, but your descendants also? This blessing that Lehi gives comes with conditions and a curse if they do not heed God. This is later fulfilled when Nephi and his people flee from Laman and his. How do the actions we take now affect the generations that come after us? How can our actions curse our offspring and cut them off from God?
After giving his blessing to Laman and Lemuel, Lehi emphasizes that we are in charge of our lives. That we must choose good or evil and God has given all men the ability to do so. He then teaches us the results of that choice by retelling the Garden of Eden story. But this time the story is framed by the coming of the Messiah. By framing it this way, Lehi is able to show us that the fall was a part of the plan, that Christ was prepared from the beginning to save mankind from inevitable death, and that man must experience opposition so that he can have joy. Joy in life, joy in the eternities, and joy in Christ.