This creed is attributed to Athanasius, the fourth century bishop of Alexandria who was the strongest defender of the doctrines of the Trinity and the divinity of Christ. It defines the doctrines of the Trinity and the nature of Christ in very concise language.
Please note that the term "catholic" with the lower case 'c' is not a reference to the Roman Catholic Church, but is a reference to the universal Christian faith, since that is how the term was originally used.
Whosoever will be saved, before all things it 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.
[here’s an example where Joseph Smith confounded the persons] it would be nice if a Mormon explained where they disagree with the Creed they say they disagree with
23 All things are delivered to me of my Father; and no man knoweth that the Son is the Father, and the Father is the Son, but him to whom the Son will reveal it. JST
3 The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and Son—
4 And they are one God, yea, the very Eternal Father of heaven and of earth.
15 Teach them that redemption cometh through Christ the Lord, who is the very Eternal Father. Amen.
Mosiah 7:27 And because he said unto them that Christ was the God, the Father of all things, and said that he should take upon him the image of man, and it should be the image after which man was created in the beginning; or in other words, he said that man was created after the image of God, and that God should come down among the children of men, and take upon him flesh and blood, and go forth upon the face of the earth—
Ether 3:14 Behold, I am he who was prepared from the foundation of the world to redeem my people. Behold, I am Jesus Christ. I am the Father and the Son. In me shall all mankind have life, and that eternally, even they who shall believe on my name; and they shall become my sons and my daughters.
For there is one Person of the Father, another of the Son, and another of the Holy Spirit. But the godhead of the Father, of the Son, and of the Holy Spirit, is all one, the glory equal, the majesty co-eternal.
Such as the Father is, such is the Son, and such is the Holy Spirit. The Father uncreated, the Son uncreated, and the Holy Spirit uncreated. The Father incomprehensible, the Son incomprehensible, and the Holy Spirit incomprehensible.
Mosiah 4:9 Believe in God; believe that he is, and that he created all things, both in heaven and in earth; believe that he has all wisdom, and all power, both in heaven and in earth; believe that man doth not comprehend all the things which the Lord can comprehend.
The Father eternal, the Son eternal, and the Holy Spirit eternal. And yet they are not three eternals, but one Eternal.
44 Now, this restoration shall come to all, both old and young, both bond and free, both male and female, both the wicked and the righteous; and even there shall not so much as a hair of their heads be lost; but everything shall be restored to its perfect frame, as it is now, or in the body, and shall be brought and be arraigned before the bar of Christ the Son, and God the Father, and the Holy Spirit, which is one Eternal God, to be judged according to their works, whether they be good or whether they be evil.
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 Spirit Almighty. And yet they are not three almighties, but one Almighty.
So the Father is God, the Son is God, and the Holy Spirit is God. And yet they are not three gods, but one God.
So likewise the Father is Lord, the Son Lord, and the Holy Spirit Lord. And yet not three lords, but one Lord.
For as we are compelled by the Christian verity to acknowledge each Person by Himself to be both God and Lord, so we are also forbidden by the catholic religion to say that there are 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 Spirit is of the Father, neither made, nor created, nor begotten, but proceeding.
So there is one Father, not three fathers; one Son, not three sons; one Holy Spirit, not three holy spirits.
And in the Trinity none is before or after another; none is greater or less than another, but all 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 worshipped.
He therefore that will be saved must think thus 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 rational soul and human flesh subsisting. Equal to the Father, as touching His godhead; and inferior to the Father, as touching His manhood; who, although He is 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 rational 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 sits at the right hand of the Father, God Almighty, from whence He will come to judge the quick and the dead. At His coming all men will rise again 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.