"SACKCLOTH. . . . A rough material made from the hair of a goat or camel. . . . In ancient sources, the term frequently appears (often alongside ASHES) within the context of A[ncient ]N[ear ]E[astern] and biblical rites of MOURNING or as an expression of repentance. . . .
"Sackcloth (along with ashes) traditionally represented an expression of mourning, . . . a sign of repentance, . . . or the judgment of God. . . ."
"ASHES. . . . Ashes are often mentioned in connection with DUST and SACKCLOTH as signs of MOURNING, GRIEF, and humiliation; . . . the application of ashes to the head and body at times of personal and national crisis, often accompanied by FASTING, indicated penitence. . . ."
The new interpreter's dictionary of the Bible, ed. Katherine Doob Sakenfeld et al. (5 vols., Nashville, TN: Abingdon Press, 2006), s.v. "Sackcloth," by Brian B. Schmidt (vol. 5, p. 16), and "Ashes," by Judith R. Baskin (vol. 1, p. 299).