If you’re a Catholic, you’ve probably seen it: a mysterious series of letters and numbers, looking for all the world like an equation, inscribed in chalk over a doorway at your parish, or at the home of a friend. Maybe you thought you could figure it out. Maybe you were too embarrassed to ask, “What the heck is that?”

If you don’t know what the chalk is all about, don’t be ashamed. You’re certainly not alone.

Epiphany (also known as Twelfth Night, Theophany, or Three Kings Day) marks the occasion of a time-honored Christian tradition of “chalking the doors.” The formula for the ritual — adapted for 2020 — is simple: take chalk of any color and write the following above the entrance of your home: 20 + C + M + B + 20.

The letters have two meanings. First, they represent the initials of the Magi — Caspar, Malchior, and Balthazar — who came to visit Jesus in His first home. They also abbreviate the Latin phrase, Christus mansionem benedicat: “May Christ bless the house.” The “+” signs represent the cross, and the “20” at the beginning and the “20” at the end mark the year. Taken together, this inscription is performed as a request for Christ to bless those homes so marked and that He stay with those who dwell therein throughout the entire year.

The chalking of the doors is a centuries-old practice throughout the world, though it appears to be somewhat less well-known in the United States. It is, however, an easy tradition to adopt, and a great practice whereby we dedicate our year to God from its very outset, asking His blessing on our homes and on all who live, work, or visit them there.

The timing for the chalking of the doors varies somewhat in practice. In some places, it is done on New Year’s Day. More commonly, it is performed on the traditional Feast of the Epiphany — the Twelfth Day of Christmas. Most often the chalking takes place after Epiphany Mass, and can be done at any church, home, or dwelling. Traditionally the blessing is done by either a priest or the father of the family. This blessing can be performed simply by just writing the inscription and offering a short prayer, or more elaborately, including songs, prayers, processions, the burning of incense, and the sprinkling of holy water.

After many Epiphany Masses, satchels of blessed chalk, incense, and containers of Epiphany water (holy water blessed with special blessings for Ephiphany) are distributed. These can then be brought home and used to perform the ritual. Another common practice is to save a few grains of the Epiphany incense until Easter, so that it can be burned along with the Easter candle.

Practicing traditions like the chalking of the doors helps us to live our Faith more concretely and serve as an outward sign of our dedication to Our Lord. Our homes are also the place where many of us will make the greatest strides in our spiritual growth, through observance of daily prayer, spiritual reading, and work offered as an oblation to God.

The chalking of the doors of a home encourages Christians to dedicate their life at home to God and to others. Seeing the symbols over our doors can help to remind us, while passing in and out on our daily routines, that our homes and all those who dwell there belong to Christ. It also serves as a reminder of welcoming the Magi gave to Jesus. We should strive to be as welcoming to all who come to our homes to visit us!

Below, we’ve provided some examples of how this ceremony can be performed.

This ceremony of the blessing of the home and inscription of the initials of the three Magi above each door can be performed either by a priest or the father of the family. The following prayer is taken from the book, The Twelve Days of Christmas, by Elsa Chaney.

The feast of manifestation, or Epiphany, is traditionally celebrated the 12th day after Christmas, January 6th. In the dioceses of the United States, according to the new calendar, this feast has been moved to the Sunday between January 2 and January 8.

Prayer: On entering the home, Leader(Priest, if present, or father of the family) : Peace be to this house.

All: And to all who dwell herein. All: From the east came the Magi to Bethlehem to adore the Lord; and opening their treasures they offered precious gifts: gold for the great King, incense for the true God, and myrrh in symbol of His burial. All Pray: The Magnificat. During the Magnificat, the room is sprinkled with holy water and incensed. After this is completed, All: From the east came the Magi to Bethlehem to adore the Lord; and opening their treasures they offered precious gifts: gold for the great King, incense for the true God, and myrrh in symbol of His burial. Leader: Our Father. . .

And lead us not into temptation All: But deliver us from evil.

Leader: All they from Saba shall come

All: Bringing gold and frankincense.

Leader: O Lord, hear my prayer.

All: And let my cry come to You. Leader: Let us pray. O God, who by the guidance of a star didst on this day manifest Thine only-begotten Son to the Gentiles, mercifully grant that we who know Thee by faith may also attain the vision of Thy glorious majesty. Through Christ our Lord. All: Amen. Leader: Be enlightened, be enlightened, O Jerusalem, for thy light is come, and the glory of the Lord is risen upon thee—Jesus Christ born of the Virgin Mary. All: And the Gentiles shall walk in thy light and kings in the splendor of thy rising, and the glory of the Lord has risen upon thee. Leader: Let us pray.

Bless, + O Lord God almighty, this home, that in it there may be health, purity, the strength of victory, humility, goodness and mercy, the fulfillment of Thy law, the thanksgiving to God the Father and to the Son and to the Holy Spirit. And may this blessing remain upon this home and upon all who dwell herein. Through Christ our Lord. All: Amen. After the prayers of the blessing are recited, each room of the home is sprinkled with Epiphany water and incensed. The initials of the Magi are inscribed upon the doors with the blessed chalk. (The initials, C, M, B, can also be interpreted as the Latin phrase “Christus mansionem benedicat” which means “Christ bless this house”.) Example: 20 + C + M + B + 20

Another possible prayer to say during your Chalking:

May all who come to our home this year rejoice to find Christ living among us; and may we seek and serve, in everyone we meet, that same Jesus who is your incarnate Word, now and forever. Amen. God of heaven and earth, you revealed your only-begotten One to every nation by the guidance of a star. Bless this house and all who inhabit it. Fill us with the light of Christ, that our concern for others may reflect your love. We ask this through Christ our Saviour. Amen. Loving God, bless this household. May we be blessed with health, goodness of heart, gentleness, and abiding in your will. We ask this through Christ our Saviour. Amen.

However you do it, it’s a rich tradition, a worthy invocation of God’s blessing, and a great conversation starter for your guests. For every person who asks about the inscription, there’s an opportunity to spread this authentically Catholic practice during the Epiphany.

Steve Skojec contributed to this article. Originally published on January 5, 2016.