Although verse 24 stresses the importance of clinging to the iron rod to reach the tree, the real message is in verse 25 when those who partake then feel shame. Although they laid hold on the iron rod, it essentially did nothing for their eternal salvation. Holding to the rod lets us exercise our agency correctly and progress, but the mere fact of holding the rod does not ensure a successful choice when we reach the tree. The iron rod is a guide, not a guarantee.
Variant: Both the original and the printer’s manuscripts have “mists of darkness” rather than “mist of darkness.” It is doubtful if this change is significant. Indeed, the original and printer’s manuscript both have “mist of darkness” in 1 Nephi 12:4.