The Sign of the Cross is the most fundamental gesture of Catholic prayer. It recalls our Baptism, professes our faith in the Trinity, and invokes God's blessing as we begin and end our prayers.
English
In the name of the Father,
and of the Son,
and of the Holy Spirit.
Amen.
Latin (Signum Crucis)
In nomine Patris,
et Filii,
et Spiritus Sancti.
Amen.
Origin: The practice is ancient. Tertullian (early 3rd century) already witnesses to Christians tracing the sign on their foreheads "in all our actions." The Catechism (no. 2157) teaches that Christians begin their day, prayers, and actions with this sacred gesture.