Trinity Sunday: Oneness and Threeness

User’s Guide to Sunday, May 30, the Solemnity of the Most Holy Trinity

Francesco Cairo (1607-1665), “The Holy Trinity”
Francesco Cairo (1607-1665), “The Holy Trinity” (photo: Register Files / Public Domain)

Sunday, May 30, is the Solemnity of the Most Holy Trinity or “Trinity Sunday.” 

Mass Readings: Deuteronomy 4:32-34, 39-40; Psalm 33:4-22; Romans 8:14-17; Matthew 28:16-20.

Happy Trinity Sunday! This is one of those majestic feasts that we ought to celebrate in a bigger way, but lack the cultural customs to do so. The origins of this feast lie in a custom in medieval monasteries to pray special prayers in honor of the Trinity on the Sunday after Pentecost, as an antidote to heresy. Pope John XXII established it as a feast for the whole Church in the early 1300s, and so it has remained. 

The Trinity is central to our faith. 

The Trinity is not just an irrelevant theoretical belief. If God is not a Trinity, Jesus and the Spirit should not be worshipped. If God is not a Trinity, then Jesus is not God, and it follows that God did not come down to save us himself. The Trinity affirms both oneness and threeness: one God, three Persons. 

Our first reading (Deuteronomy 4:32-34, 39-40) emphasizes God’s oneness, a doctrine we share with our Jewish brothers and sisters. Moses speaks to the people on the threshold of the Promised Land and reminds them: “Fix in your heart that the Lord is God … and that there is no other” (verse 39). In Africa, Asia and other parts of the world, polytheism (belief in many gods) still flourishes. We believe: There is only one God worthy of worship, the Creator, the God of Israel, incarnate in Jesus.

Our second reading (Romans 8:14-17) is a beautiful excerpt from St. Paul that illuminates the role of the three Persons in the spiritual life of the believer: “You received a Spirit of adoption, through whom we cry, ‘Abba, Father!’ … The Spirit himself bears witness … that we are children of God [the Father], and if children, then heirs … joint heirs with Christ” (verses 15-17). Simply put, the Spirit makes us share in Jesus’ own Sonship to the Father, so we can cry out with that term of intimacy Jesus himself used, “Abba! Father!” 

“Abba” is the word for “father” in Aramaic, the spoken language of the Jews of Jesus’ day, and while it doesn’t quite mean “daddy” (as sometimes claimed) it is more intimate than English’s “Father.” Only Mark records Jesus saying “Abba,” and only in Gethsemane, Our Lord’s most intense time of prayer. So the Spirit draws us into that same intense life of the Trinity that Jesus experienced, a life of self-giving love, which is demanding and even painful for us finite creatures. St. Paul reminds us that “we suffer with him so that we may also be glorified with him” (verse 17).

Our Gospel, the Great Commission at the end of Matthew, emphasizes the threeness of the Persons: “Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit, teaching them to observe all that I have commanded you.” 

The co-equality of the Persons is reflected by the fact that the names of each must be invoked for valid baptism. Judaism and even other religions perform various “baptisms” or ritual washings, but not in the name of Father, Son and Spirit. 

But recognizing the true God must result in obedience to him: “teaching them to observe all that I have commanded.”

The Church’s mission is not complete when people are simply baptized, but only when their whole life is obedient to everything Jesus taught.