The Book of Mormon records that the Nephites practiced the ancient Israelite custom of putting ashes on one's head while fasting (Mosiah 11:25). Richardson, Richardson and Bentley note that the ancient Israelites had a custom of covering the head with ashes as a means of cleansing and purification and in times of grief, mourning, and fasting (Daniel 9:3; Isaiah 58:5; Esther 4:3). They also point out that a Mayan fasting ritual is similar to this ancient Israelite practice and provides additional evidence that the Book of Mormon is true. According to Mesoamerican historian Diego de Landa, it was the custom of the Maya to cover themselves with soot or black paint while fasting. (Diego de Landa, Relacion de las Cosas de Yucatan, translated by Alfred M. Tozzer, pp. 103, 152, 165, cited in Cheesman, The World of the Book of Mormon, p. 17.) [Allen H. Richardson, David E. Richardson and Anthony E. Bentley, 1000 Evidences for the Church of Jesus Christ of Latter-day Saints: Part Two-A Voice from the Dust: 500 Evidences in Support of the Book of Mormon, p. 42]
“Sackcloth and Ashes”
According to McConkie and Millet, biblical sackcloth, which was made of goat's hair, was dark in color and coarse in texture. Traditionally it was worn by those in mourning and thus it becomes an appropriate symbol for the godly sorrow and contrition of a soul that must be a part of true repentance. The strewing of ashes upon oneself was also a symbolic gesture representing the depth of humility and the fulness of penitence. (See 1 Kings 20:31-32; Matthew 11:21.) [Joseph Fielding McConkie and Robert L. Millet, Doctrinal Commentary on the Book of Mormon, Vol. II, pp. 203-204]
Whether the "sackcloth" mentioned in Mosiah 11:25 was exactly the same as biblical sackcloth is not known, although "goats" are mentioned in Enos 1:21. One also has to wonder about the symbolism. Did the coarseness of the sackcloth symbolize the relative coarseness of the character of man with respect to the Lord's ways? And did the black ashes smeared on the skin represent a "skin of blackness"? And would the atonement of the Lord wipe clean the darkness and smooth away the coarseness? [Alan C. Miner, Personal Notes]