We Confess the Trinity in the Athanasian Creed

Those who believe it are saved
Three unified persons, but only one God
One eternal and infinite God
One Almighty God and LORD
One coequal and co-eternal God

The Athanasian Creed (Part A):

Whoever wishes to be saved must, above all else, hold to the true Christian faith. Whoever does not keep this faith pure in all points will certainly perish forever.

Now this is the true Christian faith:

We worship one God in three persons and three persons in one God, without mixing the persons or dividing the divine being.

For each person—the Father, the Son, and the Holy Spirit—is distinct, but the deity of Father, Son, and Holy Spirit is one, equal in glory and co-eternal in majesty.

What the Father is, so is the Son, and so is the Holy Spirit.

The Father is uncreated, the Son uncreated, the Holy Spirit uncreated; the Father is infinite, the Son infinite, the Holy Spirit infinite; the Father is eternal, the Son eternal, the Holy Spirit eternal; yet they are not three who are eternal, but there is one who is eternal, just as they are not three who are uncreated, nor three who are infinite, but there is one who is uncreated and one who is infinite.

In the same way the Father is almighty, the Son is almighty, the Holy Spirit is almighty; yet they are not three who are almighty, but there is one who is almighty.

So the Father is God, the Son is God, the Holy Spirit is God; yet they are not three Gods, but one God.

So the Father is Lord, the Son is Lord, the Holy Spirit is Lord; yet they are not three Lords, but one Lord.

For just as Christian truth compels us to confess each person individually to be God and Lord, so the true Christian faith forbids us to speak of three Gods or three Lords.

The Father is neither made nor created nor begotten of anyone.

The Son is neither made nor created, but is begotten of the Father alone.

The Holy Spirit is neither made nor created nor begotten, but proceeds from the Father and the Son.

So there is one Father, not three Fathers; one Son, not three Sons; one Holy Spirit, not three Holy Spirits.

And within this Trinity none comes before or after; none is greater or inferior, but all three persons are coequal and co-eternal, so that in every way, as stated before, all three persons are to be worshiped as one God and one God worshiped as three persons.

Whoever wishes to be saved must have this conviction of the Trinity.