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. As the priest applies the ashes to a person's forehead, he speaks the words: "Remember that you are dust, and to dust you shall return.” Ashes also symbolize grief, in that we have sinned and caused division from God.
Writings from the Second-century Church refer to the wearing of ashes. Priests administer ashes during Mass and all are invited to accept the ashes as a visible symbol of penance. Even non-Christians and the excommunicated are welcome to receive the ashes. The ashes are made from blessed palm branches, taken from the previous year's palm Sunday Mass, which are then burned, christened with holy water, and scented by incense.
It is important to remember that Ash Wednesday is a day of penitential prayer and fasting. It is not required that a person wear the ashes for the rest of the day, and they may be washed off after Mass. However, many people keep the ashes as a reminder until the evening. Ashes may be delivered by a priest or a family member to those who are sick or shut-in.
Following the example of the Ninevites, who did penance in sackcloth and ashes, our foreheads are marked with ashes to humble our hearts and reminds us that life passes away on Earth. The distribution of ashes comes from an ancient ceremony whereby Christians who had committed grave faults performed public penance. On Ash Wednesday, the Bishop blessed the hair shirts which they were to wear during the forty days of penance, and sprinkled over them ashes made from the palms from the previous year. Then, while the faithful recited the Seven Penitential Psalms, the penitents were turned out of the church because of their sins -- just as Adam, the first man, was turned out of Paradise because of his disobedience. The penitents did not enter the church again until Maundy Thursday after having won reconciliation by the toil of forty days' penance and sacramental absolution. Later, all Christians, whether public or secret penitents, came to receive ashes out of devotion. In earlier times, the distribution of ashes was followed by a penitential procession.