Whosoever will be saved, before all things it is necessary that he hold the catholic faith. Which faith except every one do keep whole and undefiled, without doubt he shall perish everlastingly.
And the catholic faith is this,
That we worship one God in Trinity, and Trinity in Unity;
Neither confounding the Persons, nor dividing the Substance.
For there is one Person of the Father, another of the Son, and another of the Holy Ghost.
But the Godhead of the Father, of the Son, and of the Holy Ghost is all one:
the glory equal, the majesty coeternal.
- Athanasian Creed, A Reader's Edition of the Book of Concord, 2nd edition, pg. 17
(Video done by Lutheran Satire, which is a very entertaining channel from those of the Lutheran Confession, showing that theology doesn't have to be stuffy or dry, but rather can have humor in it!)