Why do we make the sign of the cross when entering the church, at the beginning of the mass or any other prayer?

The answer is both simple and profound.  In the Sign of the Cross, we profess the deepest mysteries of the Christian Faith, the Trinity: Father, Son, and Holy Ghost, and the saving work of Christ on the Cross on Good Friday.  We mark ourselves as Christians through the Sign of the Cross.  The sign of the cross is a prayer, a blessing, and sacramental.  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”.  The sign of the cross is made using your right hand regardless of your dominant hand; you should touch your forehead at the mention of the Father, the lower middle of your chest at the mention of the Son, and the left shoulder on the word “Holy” and the right shoulder on the word “Spirit.”

The sign of the cross is a very ancient practice and prayer.  We don’t have any indication of it in Scripture, but St. Basil in the fourth century said that we learned the sign from the time of the apostles and that it was administered in baptisms.  Some scholars interpret St. Paul’s saying in Galatians 6:17 that he bears the marks of Christ on his body as his referring to the sign of the cross. The sign means a lot of things: it is a confession of faith, a renewal of baptism, a mark of discipleship, an acceptance of suffering, a defense against the devil, and a victory over self-indulgence.

When you make the sign, you are professing a mini version of the creed; you are professing your belief in the Father, in the Son and in the Holy Spirit.  When you say the words and pray in someone’s name you are declaring their presence and coming into their presence; that’s how a name is used in Scripture.

When suffering comes, the sign of the cross is a sign of acceptance.  It’s remembering that Jesus became a man and suffered for us and that we participate in Christ’s suffering.  The sign of the cross says, “I am willing to embrace suffering to share in Christ’s suffering.”

One of the main teachings of the early Church Fathers is that the sign of the cross is a declaration of defense against the devil.  When you sign yourself, you are declaring to the devil, “Hands off. I belong to Christ; he is my protection.”  It’s both an offensive and defensive tool.