The Athanasian Creed cir. fifth or sixth century

Whoever wishes to be saved must, above all, keep the Catholic faith; for unless a person keeps this faith whole and entire he will undoubtedly be lost forever.

This is what the Catholic faith teaches. We worship one God in the Trinity and the Trinity in unity; we distinguish among the persons, but we do not divide the substance. For the Father is a distinct person; the Son is a distinct person;1 and the Holy Spirit is a distinct person. Still, the Father and the Son and the Holy Spirit have one divinity, equal glory and coeternal majesty. What the Father is, the Son is, and the Holy Spirit is. The Father is uncreated, the Son is uncreated, and the Holy Spirit is uncreated. The Father has immensity, the Son has immensity, and the Holy Spirit has immensity. The Father is eternal, the Son is eternal, and the Holy Spirit is eternal. Nevertheless, there are not three eternal beings, but one eternal being. Thus there are not three uncreated beings, nor three beings having immensity, but one uncreated being and one being that has immensity.

Likewise, the Father is omnipotent, the Son is omnipotent, and the Holy Spirit is omnipotent. Yet there are not three omnipotent beings, but one omnipotent being. Thus the Father is God, the Son is God, and the Holy Spirit is God. But there are not three gods, but one God. The Father is lord, the Son is lord, and the Holy Spirit is lord. There are not three lords, but one Lord. For according to Christian truth, we much profess that each of the persons individually is God; and according to the Christian religion we are forbidden to say that there are three gods or three lords. The Father is not made by anyone. The Son is not made nor created, but he is generated by the Father alone. The Holy Spirit is not made nor created nor generated, but proceeds from the Father and the Son.

There is, then, one Father, not three fathers; one Son, not three sons; one Holy Spirit, not three holy spirits. In this Trinity, there is nothing that precedes, nothing subsequent to anything else. There is nothing greater, nothing lesser than anything else. But the entire three persons are coeternal and coequal with one another, so that, as we have said, we worship complete unity in the Trinity and the Trinity in unity. This, then, is what he who wishes to be saved must believe about the Trinity.

It is also necessary for eternal salvation that he believe steadfastly in the Incarnation of our Lord Jesus Christ. The true faith is: we believe and profess that our Lord Jesus Christ, the Son of God, is both God and man. As God he was begotten of the substance of the Father before time; as man he was born in time of the substance of his Mother. He is perfect God; and he is perfect man, with a rational soul and human flesh. He is equal to the Father in his divinity but he is inferior to the Father in his humanity. Although he is God and man, he is not two but one Christ. And he is one, not because his divinity was changed into flesh, but because his humanity was assumed to God. He is one, not at all because of a mingling of substances, but because he is one person. As a rational soul and flesh are one man, so God and man are one Christ. He died for our salvation, descended to hell, arose from the dead on the third day, ascended into heaven, sits at the right hand of God the Father almighty, and from there he shall come to judge the living and the dead. At his coming, all men are to arise with their own bodies; and they are to give an account of their lives. Those who have done good deeds will go into eternal life; those who have done evil will go into everlasting fire.

This is the Catholic faith. Everyone must believe it, firmly and steadfastly; otherwise, he cannot be saved.

[Another translation reads:]

Whosoever will be saved, before all things it is is necessary that he hold the Catholic Faith. Which Faith except everyone 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 co-eternal. Such as the Father is, such is the Son, and such is the Holy Ghost. The Father uncreate, the Son uncreate, and the Holy Ghost uncreate. The Father incomprehensible, the Son incomprehensible, and the Holy Ghost incomprehensible. The Father eternal, the Son eternal, and the Holy Ghost eternal. And yet they are not three eternals, but one eternal. As also there are not three incomprehensibles, nor three uncreated, but one uncreated, and one incomprehensible. So likewise the Father is Almighty, the Son Almighty, and the Holy Ghost Almighty. And yet they are not three Almighties, but one Almighty. So the Father is God, the Son is God, and the Holy Ghost is God. And yet they are not three Gods, but one God. So likewise the Father is Lord, the Son Lord, and the Holy Ghost Lord. And yet not three Lords, but one Lord. For like as we are compelled by the Christian verity to acknowledge every Person by Himself to be both God and Lord, so we are forbidden by the Catholic Religion, to say, there be three Gods, or three Lords. The Father is made of none, neither created, nor begotten. The Son is of the Father alone, not made, nor created, but begotten. The Holy Ghost is of the Father [and of the Son], neither made, nor created, nor begotten, but proceeding. So there is one Father, not three Fathers; one Son, not three Sons; one Holy Ghost, not three Holy Ghosts. And in this Trinity none is afore, or after other; none is greater, or less than another; but the whole three Persons are co-eternal together and co-equal. So that in all things, as is aforesaid, the Unity in Trinity and the Trinity in Unity is to be worshiped. He therefore that will be saved must thus think of the Trinity.

Furthermore, it is necessary to everlasting salvation that he also believe rightly the Incarnation of our Lord Jesus Christ. For the right Faith is, that we believe and confess, that our Lord Jesus Christ, the Son of God, is God and Man. God, of the substance of the Father, begotten before the worlds; and Man, of the Substance of His Mother, born in the world; Perfect God and perfect Man, of a reasonable soul in human flesh subsisting; Equal to the Father, as touching His Godhead; and inferior to the Father, as touching His Manhood. Who, although He be God and Man, yet He is not two, but one Christ; One, not by conversion of the Godhead into flesh, but by taking of the Manhood into God; One altogether; not by confusion of Substance, but by unity of Person. For as the reasonable soul and flesh is one man, so God and Man is one Christ. Who suffered for our salvation, descended into hell, rose again the third day from the dead. He ascended into heaven, He sitteth on the right hand of the Father, God Almighty, from whence He shall come to judge the quick and the dead. At whose coming all men shall rise with their bodies and shall give account for their own works. And they that have done good shall go into life everlasting; and they that have done evil into everlasting fire.

This is the Catholic Faith, which except a man believe faithfully, he cannot be saved.

Amen.