The sign of the cross probably originated with the early baptismal rights in which the minister would use a finger of his right hand to mark the candidates the forehead. There is no reference to this in scripture, but one of the early church fathers, Tertullian (d. after 220), says the sign of the cross dates back to the apostles. St. Augustine (d. 430) said marking oneself with the sign of the cross was a Christian’s outward profession of faith.
Originally, the sign of the cross was likened to a mark of ownership. In the ancient world, owners would mark their slaves on the forehead. Since at baptism we are “promised” to Christ, it became the tradition for Christians to sign themselves on the forehead. It is one of our oldest customs to do this just before the Gospel is proclaimed in the liturgy. This “little” sign of the cross was the practice of Christian for many centuries.
The large cross that we trace from forehead to waist and across our shoulders started later. The first dates we know are from the sixth century and might have been more broadly practiced from about the eleventh century. In the 13th century, Pope Innocent III decreed that the sign of the cross should be made with three fingers from the forehead to the chest, and from the right to the left shoulder. At a later date, the whole hand was used, and the direction changed from the left to the right shoulder. This short but beautiful prayer expresses our faith in the Trinity and also recalls our Baptismal Promise – our Promise in Christ.
Director of Worship, Church of St. Joseph