Question: Ash Wednesday comes from the ancient Jewish tradition of penance and fasting. The practice includes the wearing of ashes on one's forehead. What do the ashes symbolize? For how long after the ashes are applied must they be worn?
Bonus question: Where in the Bible is this tradition of ashes mentioned?
Answer: Ashes symbolize the dust from which God made us, grief, and repentance. They may be washed off after mass, but are often worn through the evening.
Bonus Answer: Daniel 9:3 and Jonah 3:6,10, and maybe others?
Read more:
http://www.catholic.org/lent/ashwed.php
http://thecatholicspirit.com/holy-days/lent/why-do-we-receive-ashes-on-ash-wednesday-2/