Three fingers touch the forehead, then the breast, then the shoulders, accompanied by the words "In the name of the Father, and of the Son, and of the Holy Spirit." The sign of the cross, noting Jesus’ ultimate sacrifice, is almost as old as the Catholic Church itself.
According to The Catholic Encyclopedia, evidence of this act dates to the second century, when the faithful would trace the cross with their thumb or finger on their own foreheads. Today, priests and deacons still trace with the thumb on people receiving sacraments. The faithful do the same on their own foreheads, lips and breast as the Gospel is about to be read. Priests and deacons use another type of sign of the cross — in the air — when blessing people or objects.