Trinity Sunday is a celebration in honor of the Trinity that is celebrated in many Western churches on the Sunday following Pentecost (the 50th day after Easter). This feast was celebrated on this day from as early as the 10th century. Celebration of the feast slowly spread in the churches of northern Europe, and in 1334 Pope John XXII approved it for the entire church.
Unlike other celebrations in the church’s calendar, Trinity Sunday focuses on a doctrine of the church, rather than an event. It celebrates the mystery that God exists in the three persons of the Holy Trinity. It is a day of adoration and praise of the one, eternal, incomprehensible God.
As the Companion to the Book of Common Worship (CBCW) states,
“Trinity Sunday, in a sense, synthesizes all we have celebrated over the past months which have centered on God’s mighty acts: Christmas-Epiphany celebrating God’s taking flesh and dwelling among us in Jesus Christ; Easter celebrating Christ’s death and resurrection for us; Pentecost celebrating God the Holy Spirit becoming our Sanctifier, Guide, and Teacher. It is, therefore, a fitting transition to that part of the year when Sunday by Sunday the work of God among us is unfolded in a more general way. [1]
The Core of Christian Teaching
If there is any doctrine that makes Christianity Christian, it is surely the doctrine of the Trinity. In the Lord’s last day of earthly life, when the world was about to be completely turned upside down on the disciples, the Lord chose to spend that time in the Upper Room teaching them about the mystery of the Trinity. Surely this highlights how absolutely critical and central this teaching is to the Christian faith. [2] It is only right to dedicate a Sunday to the explicit worship and adoration of the Holy Trinity because the Trinity is at the very heart of everything we are and do as Christians. The church’s earliest creeds were crafted to protect this most important teaching against the false ideas of heretics. If you look at the Apostles’ Creed, Nicene Creed, or the Athanasian Creed, all are dealing with the doctrine of the Trinity and two of them even take a very clear Trinitarian structure.
The Athanasian Creed makes this assertion on the centrality of this doctrine:
This is the catholic faith: That we worship one God in trinity and the trinity in unity, neither blending their persons, nor dividing their essence. For the person of the Father is a distinct person, the person of the Son is another, and that of the Holy Spirit, still another. But the divinity of the Father, Son, and Holy Spirit is one, their glory equal, their majesty coeternal. [3]
What is this Doctrine?
Though volumes have been written about the Trinity, Augustine summarized this doctrine in seven statements that were later enshrined in the well-known symbol called the Shield of the Trinity. The seven statements are the following:
(1) There is only one God.
(2) The Father is God.
(3) The Son is God.
(4) The Holy Spirit is God.
(5) The Father is not the Son.
(6) The Son is not the Holy Spirit.
(7) The Holy Spirit is not the Father.
Others have suggested four essential affirmations that put the same truths positively:
(1) There is one and only one true and living God.
(2) This one God eternally exists in three persons—God the Father, God the Son, and God the Holy Spirit.
(3) These three persons are completely equal in attributes, each with the same divine nature.
(4) While each person is fully and completely God, the persons are not identical. [4]
One Day and Every Day
This Sunday millions will gather across this globe to worship the Holy Trinity. We will sing hymns like the well known hymn “Holy, Holy, Holy” by Reginald Heber.
Holy, holy, holy! Lord God Almighty!
All thy works shall praise thy name, in earth, and sky, and sea;
Holy, holy, holy! merciful and mighty!
God in three Persons, blessed Trinity.
While it is right and good to set aside a day to explicitly honor and glorify the Holy Trinity, let our worship not be confined to that one day. Again, in the words of the CBCW, “In celebrating Trinity Sunday, remember that every Lord’s Day is consecrated to the triune God. On the first day of the week, God began creation. On the first day of the week, God raised Jesus from the grave. On the first day of the week, the Holy Spirit descended on the newly born church. Every Sunday is special. Every Sunday is a day of the Holy Trinity.” [5]
[1] Companion to the Book of Common Worship (Geneva Press, 2003, 149-150). As quoted here: https://pcusa.org/about-pcusa/agencies-entities/interim-unified-agency/ministry-areas/theology-worship/worship/christian-year/trinity-sunday.
[2] Kevin DeYoung makes these observations in is recent book Daily Doctrine: A One-Year Guide to Systematic Theology (Wheaton, IL: Crossway, 2024), 60-61.
[3] See the Athanasian Creed as translated here: https://www.crcna.org/welcome/beliefs/creeds/athanasian-creed.
[4] Erik Theonnes, “Biblical Doctrine: An Overview,” in ESV Study Bible (Wheaton, IL: Crossway, 2008), 2513.
[5] Companion to the Book of Common Worship (Geneva Press, 2003, 149-150). As quoted here: https://pcusa.org/about-pcusa/agencies-entities/interim-unified-agency/ministry-areas/theology-worship/worship/christian-year/trinity-sunday.
