What two guys in the Book of Helaman stood in the midst of a fire but were not harmed?

Helaman's sons, Nephi and Lehi

(Twice in the same chapter!)

Nephi and Lehi were encircled about as if by fire ... Nevertheless, Nephi and Lehi were not burned; and they were as standing in the midst of fire and were not burned. Helaman 5:23

Nephi and Lehi ... were as if in the midst of a flaming fire, yet it did harm them not. Helaman 5:44