Ash Wednesday is a day of repentance and it marks the beginning of Lent. Ashes were used in ancient times, according to the Bible, to express mourning. Dusting oneself with ashes was the penitent's way of expressing sorrow for sins and faults. An ancient example of one expressing one's penitence is found in Job 42:3-6. Job says to God: "I have heard of thee by the hearing of the ear: but now mine eye seeth thee. Wherefore I abhor myself, and repent in dust and ashes." (vv. 5-6, KJV) Other examples are found in several other books of the Bible including, Numbers 19:9, 19:17, Jonah 3:6, Matthew 11:21, and Luke 10:13, and Hebrews 9:13.
However, some Christians who do not celebrate Ash Wednesday say that the practice is not consistent with Scripture and is of pagan origin. They usually cite Matthew 6:16–18, where Jesus gave prescriptions for fasting: "And whenever you fast, do not look dismal, like the hypocrites. Truly I tell you, they have received their reward. But when you fast, put oil on your head and wash your face, so that your fasting may be seen not by others but by your Father who is in secret; and your Father who sees in secret will reward you." (NRSV) These groups argue that Jesus warned against fasting to gain favor from other people and that he also warned his followers that they should fast in private, not letting others know they were fasting. For these reasons, some Christian denominations do not endorse the practice. Others, however, point out that this very passage from Matthew is the one, not coincidentally, that is appointed by the Revised Common Lectionary to be read on Ash Wednesday. They might also clarify that the ashen Cross on the forehead does not represent the fast, but the mortal (fallen) condition of human existence. And they would refer to Jesus' words whereby he expected people to repent using sackcloth and ashes: "Woe to you, Korazin! Woe to you, Bethsaida! For if the miracles that were performed in you had been performed in Tyre and Sidon, they would have repented long ago, sitting in sackcloth and ashes." (Luke 10:13; see also Matthew 11:21)