My own denomination is no exception to the orthodox Christian faith. Our very first Article of Faith confesses our belief in the Triune God. Additionally, in our Manual's "Historical Statement," we state that the Church of the Nazarene ". . . receives the ecumenical creeds of the first five Christian centuries as expressions of its own faith." Along side the Apostles' Creed and the Nicene Creed, we find that creed which John Wesley identifies as the best explication of the Trinity he ever saw (cf., his sermon "On the Trinity"), that is the so called Athanasian Creed (or Quicunque Vult) written, most likely within the fifth-century.
The words at the beginning and conclusion of the creed tying the necessity of assent to this faith with salvation have caused much difficulty for many. However, according to Ray Dunning, "Edmund J. Fortman says that it is not suggesting that the 'Catholic faith' is merely an intellectual assent but rather that it involves the 'worship of one God in Trinity, and Trinity in Unity'" (Grace, Faith and Holiness, 226). Wesley, himself, said, "I am far from saying, he who does not assent to this 'shall without doubt perish everlastingly.' For the sake of that an another clause, I, for some time, scrupled subscribing to that creed; till I considered,(1.) That these sentences only relate to wilful, not involuntary, unbelievers; to those who, having all the means of knowing the truth, nevertheless obstinately reject it: (2.) That they relate only to the substance of the doctrine there delivered; not the philosophical illustrations of it" ("On the Trinity"). - Whether one still has trouble with those lines, even after Fortman's and Wesley's explanation, the Athanasius Creed is still a wonderfully thorough confession of Trinitarian faith.
Although, it has been said that it is far too long for liturgical use, I do know at least one Lutheran pastor whose congregation uses it every Trinity Sunday (and I'm sure they are not alone).
I strongly encourage those who are unfamiliar with the creed to read it by clicking, here. (Sorry, it's a bit too long for me to reproduce on my blog.)
Please join me in this prayer from the Book of Common Prayer:
Almighty and everlasting God, you have given to us your servants grace, by the confession of a true faith, to acknowledge the glory of the eternal Trinity, and in the power of your divine Majesty to worship the Unity: Keep us steadfast in this faith and worship, and bring us at last to see you in your one and eternal glory, O Father; who with the Son and the Holy Spirit live and reign, on God, for ever and ever. Amen.