Boyd’s Bible Dictionary:
To sprinkle with or sit in ashes, marked humiliation, grief, and penitence (Gen. 18:27; 2 Sam. 13:19; Esth. 4:3; Job 2:8; Jer. 6:26; Lam. 3:16; Matt. 11:21). The altar ashes, when a red heifer was sacrificed, were watered and used for purifying the unclean (Num. 19:17-22).
Concise Bible Dictionary:
Ashes, mostly from burnt wood, were used as a sign of sorrow or mourning, either put on the head (2 Sam. 13:19), or on the body with sackcloth (Esther 4:1; Jer. 6:26; Lam. 3:16; Matt. 11:21; Luke 10:13); or strewn on a couch on which to lie (Esther 4:3; Isa. 58:5; Jonah 3:6). To eat ashes expresses great sorrow (Psa. 102:9); and to be reduced to them is a figure of complete destruction (Ezek. 28:18; Mal. 4:3); to feed on them tells of the vanities with which the soul may be occupied (Isa. 44:20). “Dust and ashes” was the figure Abraham used of himself before Jehovah (Gen. 18:27); and Job said he had become like them by the hand of God (Job 30:19). For the ashes of the Red Heifer see HEIFER.
Strong’s Dictionary of Hebrew Words:
Meaning:
from an unused root meaning to bestrew; ashes