The symbolic sign of the crucifixion. The writings of the fathers and the oldest liturgies clearly indicate the use of the sign of the cross as an integral part of the service or the sacrament. “Unless the sign of the cross is made either on the foreheads of the faithful, or on the water itself wherewith they are regenerated, or on the oil with which they are anointed with chrism, or on the with which they are nourished, none of these things is duly performed” (Saint Augustine, Homily 118 on 19:24).

The sign of the cross takes various forms, each having its own interpretation. It may be made with the right thumb when crossing oneself, and the right forefinger when crossing other people or things. This can be interpreted as a sign of the oneness of God, or a reference to Christ’s saying, “But if it is by the finger of that I cast out demons, then the of God has come upon you” (Lk. 11:20). It may also be taken as a reference to the system of purification according to Mosaic law, in which the used his finger (Lv. 14:16); to the two tablets of the testament written by the finger of God (Ex. 31:18); or to Jacob’s ladder (Gn. 28:12) symbolizing the cross on which Jesus Christ rose to heaven.

Using three fingers indicates the Holy Trinity, and five fingers indicates the five wounds suffered by Jesus Christ on the cross.

The form of the sign of the cross has developed since the early days of Christianity, when it used to be made on the forehead once or thrice; then on the forehead, the heart, and the arm. “The sign of the cross is on our brow and on our heart. It is on our brow that we may always confess Christ, on our heart that we may always love Him, on our arm that we may always work for Him” (Ambrose, De Isaac et Anima 8). Later it became customary to make the sign on the forehead (in the name of God), the mouth (in the name of Jesus Christ of God), and on the heart (in the name of the Holy Spirit).

From the sixth century onward the sign of the cross settled in the form now common to us, that is, with the thumb crossing the forefinger of the right hand, we touch the forehead, the chest, the left shoulder, and the right shoulder.