Response: The sign of the cross—an immemorial Christian custom first mentioned in writing at the beginning of the third century—signifies the grace of redemption and
strengthens us (cf. 1 Cor.1:23).
Discussion: The Catechism of the Catholic Church discusses the sign of the cross in the context of its treatments of the Second Commandment and the Sacrament of Baptism.
The Christian begins his day, his prayers, and his activities with the sign of the cross: “in the name of the Father and of the Son and of the Holy Spirit. Amen." The baptized person dedicates the day to the glory of God and calls on the Savior’s grace which lets him act as a child of the Father. The sign of the cross strengthens us in temptations and difficulties (no. 2157).
The sign of the cross, on the threshold of the celebration [of the Sacrament of Baptism], marks with the imprint of Christ the one who is going to belong to him and signifies the grace of the redemption Christ won for us by his cross (no. 1235, emphasis in text).
The first written mention of the sign of the cross occurs in Tertullian’s fascinating discussion of unwritten Tradition (De Corona Militis, A.D. 204). Tertullian describes the sign of the cross as a long-established custom:
And how long shall we draw the saw to and fro through this line, when we have an ancient practice, which by anticipation has made for us the state, i.e., of the question? If no passage of Scripture has prescribed it, assuredly custom, which without doubt flowed from tradition, has confirmed it. For how can anything come into use, if it has not first been handed down?…
At every forward step and movement, at every going in and out, when we put on our clothes and shoes, when we bathe, when we sit at table, when we light the lamps, on couch, on seat, in all the ordinary actions of daily life, we trace upon the forehead the sign (Chapter III, emphasis added).
Numerous texts from the next three centuries demonstrate that the sign of the cross was a widespread practice in the early Church. These texts are summarized in The Catholic Encyclopedia (1912):
Thus St. Cyril of Jerusalem in his Catecheses (xiii, 36) remarks: “let us then not be ashamed to confess the Crucified. Be the cross our seal, made with boldness by our fingers on our brow and in every thing; over the bread we eat and the cups we drink, in our comings and in goings; before our sleep, when we lie down and when we awake; when we are travelling, and when we are at rest."
The course of development seems to have been the following. The cross was originally traced by Christians with the thumb or finger on their own foreheads. This practice is attested by numberless allusions in Patristic literature, and it was clearly associated in idea with certain references in Scripture, notably Ezech., ix, 4 (of the mark of the letter Tau); Ex., xvii, 9-14; and especially Apoc., vii 3; ix, 4; xiv, 1. Hardly less early in date is the custom of marking a cross on objects—already Tertullian speaks of the Christian woman “signing" her bed (cum lectulum tuum signas, “Ad
uxor.," ii, 5) before retiring to rest-and we soon hear also of the sign of the cross being traced on the lips (Jerome, “Epitaph. Paulæ") and on theheart (Prudentius, “Cathem.," vi, 129). Not unnaturally if the object were more remote, the cross which was directed towards it had to be made in the air. Thus Epiphanius tells us (Adv. Hær., xxx, 12) of a certain holy man Josephus, who imparted to a vessel of water the power of overthrowing magical incantations by “making over the vessel with his finger the seal of the cross" pronouncing the while a form of prayer. Again half a century later
Sozomen, the church historian (VII, xxvi), describes how Bishop Donatus when attacked by a dragon “made the sign of the cross with his finger in the air and spat upon the monster." All this obviously leads up to the suggestion of a larger cross made over the whole body, and perhaps the earliest example which can be quoted comes to us from a Georgian source, possibly of the fourth or fifth century. In the life of St. Nino, a woman saint, honored as the Apostle of Georgia, we are told in these terms of a miracle worked by her: “St. Nino began to pray and entreat God for a long time. Then she took her (wooden) cross and with it touched the Queen’s head, her feet and her shoulders, making the sign of the cross and straightway she was
cured" (Studia Biblica, V, 32).
In the sixth century, the sign of the cross came to be made with two fingers (the index finger and middle finger, or the thumb and the index finger) as a confession of Catholic teaching that Christ had two wills and two natures. Later, the sign of the cross was made with three fingers (the thumb, index finger, and the middle finger) to confess the Blessed Trinity, while the ring finger and little finger pressed against the palm signified the two natures and wills of Christ.
In both East and West, the sign of the cross was made from right to left until the Middle Ages. Father Cassian Folsom, O.S.B., President of the Pontifical Liturgical Institute, explained the development of the current Western practice (left to right) in a 1997 talk:
It’s interesting to note that in the thirteenth century, Pope Innocent III (contemporary with St. Francis of Assisi) instructed the faithful on the meaning of the sign of the cross in these words: “The sign of the cross is made with three fingers, because the signing is done together with the invocation of the Trinity. This is how it is done: from above to below, and from the right to the left, because Christ descended from the heavens to the earth, and from the Jews (right) he passed to the Gentiles (left).
Note that Pope Innocent is describing what the custom was in the West. In the thirteenth century the East and the West still made the sign of the cross in the same way. The pope goes on to say: “Others, however, make the sign of the cross from the left to the right, because from misery (left) we must cross over to glory (right), just as Christ crossed over from death to life, and from Hades to Paradise. [Some priests] do it this way so that they and the people will be signing themselves in the same way. You can easily verify this—picture the priest facing the people for the blessing—when we make the sign of the cross over the people, it is from left to right."
So the people, imitating the blessing of the priest, began to sign themselves from left to right. Be that as it may, centuries have gone by since then, and we in the West make the sign of the cross from left to right, with the palm open.
In Christifideles Laici, the 1988 apostolic exhortation on the vocation and mission of the lay faithful in the Church and in the world, Pope John Paul II wrote briefly of the sign of the cross:
“Christian, be aware of your nobility!" Every year, on Easter night, Christians are invited to remember their Baptism. It is like a great collective anniversary of the Sacrament once received, as a child or as an adult. It is an opportunity to recall a personal event which leaves an everlasting mark on our life. It is an opportunity to relive more intensely the commitment taken that day and revive the sap received from the true vine (cf. Jn. 15,5). The aspersion at the beginning of Sunday Mass is also a reminder of the Baptism received and the promise made by the Lord: “I will wash you with pure water and you will be purified" (Ezek. 36,25). And every time we make the sign of the cross with holy water, we are reminded as Christians of our baptism. “The call to holiness is rooted in Baptism and proposed anew in the other Sacraments, principally in the Eucharist. Since Christians are reclothed in Christ Jesus and refreshed by his Spirit, they are ‘holy.’ They therefore have the ability to manifest this holiness and the responsibility to bear witness to it in all that they do" (no. 16).
Most Western Christians outside the Catholic Church do not cross themselves in prayer. The sign of the cross is a fundamental sign of the Catholic faith, one of the first learned by a child and one of the last made before death. Through the Cross of Jesus Christ, we are given the grace to be the salt of the earth and the light of the world. If we are to conquer the world from within, then let us conquer by this sign.