Despite the Christians' reticence to use the cross as a public symbol before the fourth century, they did make wide use of it as early as the second and third centuries to sign themselves on the forehead. In the second century Tertullian reorts: "In all our travels and ovements, in all our coming in and going out,... whatever employment occupies us, we mark our foreheads with the sign of the cross." In the fourth century St. Cyril of Jerusalem writes, "Let us not be ashamed ot confess the Crucified. Let the cross be our seal, made with boldness by our fingers on our brow and in everything..."|
By the sixth century in the East, probably due to the raging Monophysite heresy which denied the double nature of Christ as both God and man, two fingers began to be used to trace the sign of the cross now no longer on the forehead but more boldly with a larger sign made on the body. The succeeding centuries saw further modifications emanate from Eastern tradition because of a desire to profess more explicitly the belief in the triune God and thc double nature in Christ. The thumb and two fingers were extended to symbolize the Trinity while the ring finger and the little finger were folded back on the palm to profess the God/Man, Jesus Christ.
This newer usage also spread to the Western Church where we read Pope Leo IV, writing in the middle of the ninth century, instructing his clergy: "Sign the chalice and the host with a proper cross ...with two fingers outstretched and the thumb hidden within them, by which the Trinity is symbolized. Take heed to make this sign rightly." In the thirteenth century Pope Innocent III directed most explicitly that the sign of the cross be made with three fingers from the forehead to the breast and from the right to the left shoulder, the actual way it still is made by the majority of Eastern Christians. The Western Church retained this ancient form till about the fourteenth century when gradually the open hand was introduced and the sign began to be made in an inverted fashion, from left to right, perhaps mistakenly following the lead of the priest who in blessing inverts his movement so it would be seen correctly by the congregation before him.
Eastern Orthodox and Eastern Catholics place great emphasis on the sign of the cross as a profession of faith in the three basic doctrines of Christianity: the Holy Trinity, the double nature in Christ and the mystery of redemption. This act of faith in the teachings of Christianity is also an act of consecration to God of all human activities: thoughts, affections, actions.
The gesture is presently made by joining the fingers (thumb, index and middle finger together and erect; third and little finger down on the palm) and lifting the hand first to the forehead, then to the breast, to the right and then to the left shoulder. In the Scriptures right generally represents good and left evil, and in the Creed the Son is said to sit at the right hand of the Father, thus the signing of the right shoulder first. Eastern Christians sign themselves often especially at every mention of the name of the Holy Trinity and in conjunction with the metany or bow made to reverence holy things such as the altar or an icon.