One of the first prayers we learn as children is the sign of the cross: "In the name of the Father, and of the Son, and of the Holy Spirit." Parents teach their children how to trace the cross on their bodies with this prayer. Our whole body person is involved in this prayer. Today's gospel records the words of Jesus we use at each Baptism: "baptizing them in the name of the Father, and of the Son, and of the Holy Spirit." This Trinitarian formula has been around since at least 80 AD when Matthew wrote his gospel.
The mystery of the Trinity is the central mystery of our faith and our life. All of the other mysteries of our faith flow from this one. All of our Christian living centers around this divine mystery. We experience God as the Creator and Source of all life. We are redeemed by the death of resurrection of Christ. We constantly experience the guidance of the Holy Spirit. When are you most aware of these three "persons" of God?