Ash Wednesday is one of the most significant days in the liturgical calendar. Ash Wednesday marks the beginning of Lent, a season of prayer, fasting and alms-giving. 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." Alternatively, the priest may speak the words, "Repent and believe in the Gospel." Ashes also symbolize grief, in this case, grief that we have sinned and caused division from God, and are also a visible sign of penance. Reference: catholic.org