It is customary, especially in Central Europe, for the faithful to bless their houses
at the Epiphany with blessed chalk. They write over their front door:
20 + C + M + B + 13. Obviously, the digits,
which appear at the beginning and end of the line, designate the new year.
‘CMB’ stands for the traditional names of the Magi (Caspar, Melchior and Balthasar)
and also signifies the Latin prayer Christus Mansionem Benedicat or
‘May Christ bless this dwelling!’
The inscription is made above the front door or porch,
so that all who enter and depart the home
may enjoy God’s blessing.
It also provides a very public witness to the Faith.
In any case, these initials over our doorway serve to remind
us of who the Magi saw in that
how they saw Him. They remind us to adore Him as they did.
Here is the prayer that was used to bless the chalk:
O Lord God, bless this chalk that it may be used for the salvation of the human race.
Through the invocation of Thy most Holy Name grant that whoever shall take of
this chalk and write with it upon the doors of his house the names of Thy saints,
Caspar, Melchior and Balthasar, may through their merits and intercession
receive health of body and protection of soul. Through Christ our Lord. Amen.