From the Roman Breviary. It recalls Phil. 3:18, "For many, as I have often told you and now tell you even in tears, conduct themselves as enemies of the cross of Christ. "
PER signum Crucis de inimicis nostris libera nos, Deus noster.
BY the sign of the cross deliver us from our enemies, O our God.
In nomine Patris, et Filii, et Spiritus Sancti. Amen.
In the name of the Father, and of the Son, and of the Holy Spirit. Amen.