The early Christians were always eager to develop signs and symbols that
summarized the great mysteries of the Faith. In the Sign of the Cross, two
immense truths are signified together, namely the mystery of the Blessed
Trinity, Father, Son and Holy Spirit, and the misery and humiliation of the
Crucifixion. Spontaneously they drew this holy sign everywhere,
accompanied by any one of the following words: Sign of Christ; In the
Name of Jesus; or In the Name of the Father and of the Son and of the
Holy Spirit.
Constantine, before his great victory in the battle of Milvian Bridge (312
AD), which brought him to power as the first Christian Roman Emperor,
saw in the sky a cross with the words In Hoc Signo Vincesin this sign
you shall conquer. The victory of every Christian is achieved always
through the power of the Cross.
The Fathers
Tertullian, The Crown 3, 2 (211 AD)
At every forward step and movement, when coming in and going out,
when putting on our clothes, when putting on our shoes, when bathing,
when at table, when lighting the lamps, when reclining, when sitting, in all
the ordinary occupations of our daily lives, we furrow our forehead with
the sign.
St. Athanasius, Treatise on the Incarnation of the Word 47, 2 (c. 318
AD)
And while in times past demons, occupying springs or rivers or trees or
stones, cheated men by deceptive appearances and imposed upon the
credulous by their juggleries, now, after the divine coming of the Word, an
end is put to their deceptions. For by the sign of the cross, a man but using
it, their wiles are put to flight.
St. Cyril of Jerusalem, Catechetical Lectures 15, 22 (c. 350 AD)
But whatlest a hostile power dare to counterfeit itis the sign of His
coming? And then shall appear, He says, the sign of the Son of Man in
the heavens. Christs own true sign is the cross. The sign of a luminous