Ash Wednesday comes from the ancient Jewish tradition of penance and fasting. The practice includes the wearing of ashes on the head. The ashes symbolize the dust from which God made us. The ashes are applied to a person's forehead in the sign of the cross with the words: "
Remember that you are dust, and to dust you shall return."
Writings a far back as from the Second-century Church refer to the wearing of ashes.
