Feastday: 22 February
At the beginning of Lent, on Ash Wednesday, ashes are blessed during Mass, after the homily. The blessed ashes are then "imposed" on the faithful as a sign of conversion, penance, fasting and human mortality. The ashes are blessed at least during the first Mass of the day, but they may also be imposed during all the Masses of the day, after the homily, and even outside the time of Mass to meet the needs of the faithful. Priests or deacons normally impart this sacramental, but instituted acolytes, other extraordinary ministers or designated lay people may be delegated to impart ashes, if the bishop judges that this is necessary. The ashes are made from the palms used at the previous Passion Sunday ceremonies. — Ceremonies of the Liturgical Year, Msgr. Peter J. Elliott
The act of putting on ashes symbolizes fragility and mortality, and the need to be redeemed by the mercy of God. Far from being a merely external act, the Church has retained the use of ashes to symbolize that attitude of internal penance to which all the baptized are called during Lent. — Directory on Popular Piety and the Liturgy
Ashes may also be sprinkled on the top of
the head, as shown in this 1881 Polish painting.
From the very early times the commemoration of the approach of Christ's passion and death was observed by a period of self-denial. St. Athanasius in the year 339 enjoined upon the people of Alexandria the 40 days' fast he saw practiced in Rome and elsewhere, "to the end that while all the world is fasting, we who are in Egypt should not become a laughing stock as the only people who do not fast but take our pleasure in those days." On Ash Wednesday in the early days, the Pope went barefoot to St. Sabina's in Rome "to begin with holy fasts the exercises of Christian warfare, that as we do battle with the spirits of evil, we may be protected by the help of self-denial."
— Daily Missal of the Mystical Body