In the wilderness, Lehi has a vision filled with symbolism that includes the tree of life. In his vision he struggles for some time in the dark before finally making his way to the tree. He eats or partakes of its fruit and desires his family to do likewise. He sees a rod of iron, a strait and narrow path, and the mists of darkness that enshroud men. Sariah, Nephi, and Sam eat the fruit, but Laman and Lemuel refuse.
Based on 1 Nephi 8.
The Book of Mormon: Another Testament of Jesus Christ