1 Nephi 1:6

And it came to pass as he prayed unto the Lord, there came a pillar of fire and dwelt upon a rock before him; and he saw and heard much; and because of the things which he saw and heard he did quake and tremble exceedingly.

Important Words
pillar of fire: this may be comparable with what happened to Moses and may signal to Lehi that he is about to embark on his own "Exodus".

Commentary
As Lehi prayed, he beheld a pillar of fire dwelling upon a rock in front of him (1 Nephi 1:6). From this pillar Lehi saw and heard many powerful things, but Nephi does not elaborate on who or what Lehi saw in this pillar of fire. Joseph Smith described how God, angels, and spirits appear in fiery manifestations; he taught, for instance, that "spirits can only be revealed in flaming fire and glory." From ancient sources, too, one learns that the appearance of fire, especially a pillar of fire, was a frequent mode of heavenly manifestation, sometimes of God and other times of his messengers or of the holy beings who surrounded him. God appeared to Moses in a burning bush (Exodus 3:2) and on a flaming Mount Sinai (Exodus 19:18); he also appeared over the tabernacle at night in a fire (Numbers 9:15) and over the door of the tabernacle by day in a similar "pillar of a cloud" (Deuteronomy 31:15). On some occasions in the Old Testament, fire was associated with God's messengers, especially those emanating from God's council (discussed further below; see, e.g., Psalm 104:4), whose fiery description can be compared with the appearance of Moroni in Joseph Smith—History 1:30–32; in other ancient accounts, fire was used to combat God's enemies. Thus, we cannot be certain who or what Lehi saw in the pillar of fire that appeared to him. Lehi could have seen God in this pillar, but since Lehi's vision of God himself is reported as the next stage of the vision, it seems more likely to me that what he beheld at this time was a messenger of God whose threatening words and presence, perhaps summoning Lehi, caused Lehi to "quake and tremble exceedingly" (1 Nephi 1:6).1