Until the revisions of the 1970’s, Trinity Sunday was the hinge of the Church Year. That was the day the first half of the cycle (Advent through Pentecost) reached its culmination and turning point. All the revelation about God covered in those seasons find their apex in the doctrine of the Trinity: God is One and Three. As the Collect of the Day begins:
ALMIGHTY and everlasting God, who has given unto us your servants grace, by the confession of a true faith, to acknowledge the glory of the eternal Trinity, and in the power of the Divine Majesty to worship the Unity…
But this day is also a turning point. We have not only received this faith throughout the year to confess and worship God, but also:
We beseech thee, that this holy faith may evermore be our defence against all adversities; who livest and reignest, one God, world without end. Amen.
That is what the season of Trinitytide used to do: unfold like a discipleship course in how this faith may be our defence against all adversities.
I beseech you, readers, if you have the slightest interest in Anglican Prayer Book spirituality and history, to take a look at this essay: http://www.lectionarycentral.com/trinity/Phillips.html It brilliantly lays out how the season after Trinity served as a multi-layered course of dealing with our chief adversary: sin. The life and doctrines of Jesus are presented with Epistle lessons that together work to demolish our pride, our lusts, all our vices. There are, for sure, other ways to analyze the Trinity season, but the general agreement is that it’s an application of the teachings of the first half of the year to help us conform our lives thereto.
It’s popular now to say that the first half of the year is “the story of Jesus” and the second half is “the story of the Church.” This is wrong. The first half is the story (or better, doctrines) of God, and the second half is the application of the story/doctrines of God to us. Trinity Sunday is the hinge: it sums up all the teaching about the Father, Son, and Spirit, and presents it to us to believe, worship, and follow.
Enough with the theory, now for some advice.
how to mark Trinity Sunday
A fairly long-standing tradition, now recommended or encouraged in the general rubrics at the end of the Communion service in the 2019 Prayer Book, is to say the Athanasian Creed in place of the Nicene at the Communion Service on Trinity Sunday. It is uncomfortably long, for the average worshiper, but a paltry once a year won’t kill them. Plus, it’s honestly the best teaching tool we have when it comes to spelling out the doctrine of the Trinity without falling into one of many accidental heresies. The 1662 Prayer Book called for this Creed to be read at Morning Prayer about 13 times a year, so once a year on Trinity Sunday is really quite lenient in that light!
If you haven’t used the Great Litany with your congregation in a while, that’s another possibility to consider for this day. Its strong beginning with a Trinitarian invocation is a standard staple of Christian prayer, and extemporanous prayer these days very easily falls into Trinitarian confusion – addressing Jesus yet ending with “in Jesus’ name we pray”, or mindlessly switching from “Father-God” to “Jesus” as if it’s the same Person. The Great Litany, or indeed any collect or liturgical prayer, can be a helpful teaching example of how to pray in an orthodox manner, rightly praising the triune God without confusing the Persons or denying the Unity.
There are lots of hymns that address God as Trinity, verse by verse. If you’ve got an Anglican hymnal then the “general hymns” section usually starts with such hymns. (If you’ve got a generic Protestant hymnal, that could be a problem here.) If you opt for contemporary praise music, take care to make sure the lyrics handle the doctrine of the Trinity rightly; it’s very easy to make theological mistakes here!
Last of all, for you preachers out there, for God’s sake (literally), preach the doctrine of the Trinity. Yes it’s complicated; yes it’s difficult; yes it’s easily seen as boring, or even stilted and of minor importance. But this is basic Christian dogma; the doctrine of who & what God is the foundation of all Christian teaching. If we don’t get it right, our congregations definitely won’t get it right, and eventually the whole church will be the sicker for it. Grab a hold of the many resources in the liturgy that you’ve got, use them to your fullest advantage, and disciple your flock!