Constitution 1, De fide catholica (1215), Denzinger nos. 428-430

We firmly believe and simply confess that there is one only true God, eternal, immeasurable and unchangeable, incomprehensible, almighty and ineffable, Father and Son and Holy Spirit: three Persons indeed, but one essence, substance or nature altogether simple. The Father from none, the Son from the Father alone, and the Holy Spirit equally from both: without beginning, always and without end; the Father begetting, the Son being born, and the Holy Spirit proceeding; consubstantial and coequal and coalmighty and coeternal; one principle of all things; creator of all things visible and invisible, spiritual and corporeal; who by his almighty power from the beginning of time made together out of nothing both orders of creature, the spiritual and the corporeal, that is the angelic and the earthly, and thereafter the human, as it were common to both, composed of spirit and body. For the devil and the other demons were indeed created by God good in their nature, but they made themselves evil of their own doing. Man however sinned at the suggestion of the devil.

This Holy Trinity, undivided according to its common essence and distinct according to the properties of the Persons, gave to the human race the doctrine of salvation, first through Moses and the holy Prophets and his other servants, according to the most orderly disposition of the times. And at the last the only-begotten Son of God, Jesus Christ, made flesh by the whole Trinity in common, conceived of Mary ever Virgin by the co-operation of the Holy Spirit, made true man, composed of a rational soul and human flesh, one Person in two natures, showed more plainly the way of life. Who, although according to his divinity he is immortal and impassible, the same according to his humanity was made passible and mortal; who also, for the salvation of the human race, having suffered and died upon the wood of the cross, descended to the realms below, rose again from the dead and ascended into heaven — but he descended in the soul and rose again in the flesh, and ascended alike in both — to come at the end of the world, to judge the living and the dead, and to render to each according to his works, to the reprobate as to the elect: who shall all rise again with their own bodies, which they now bear, that they may receive according to their works, whether these have been good or evil; the one everlasting punishment with the devil, and the other everlasting glory with Christ.

There is moreover one universal Church of the faithful, outside which no one at all is saved; in which Jesus Christ himself is both priest and sacrifice, whose body and blood are truly contained in the sacrament of the altar under the species of bread and wine, the bread having been transubstantiated into the body and the wine into the blood by divine power, so that, to accomplish the mystery of unity, we ourselves may receive of what is his what he himself received of what is ours. And this sacrament no one at all can confect but a priest who has been rightly ordained according to the keys of the Church, which Jesus Christ himself granted to the Apostles and their successors. But the sacrament of baptism — which is consecrated in water at the invocation of God and the undivided Trinity, namely of the Father and of the Son and of the Holy Spirit — rightly conferred by anyone in the form of the Church, profits unto salvation both little ones and adults. And if anyone, after receiving baptism, has fallen into sin, he can always be restored through true penance. Moreover not only virgins and the continent, but also the married, pleasing God by right faith and good works, deserve to come to eternal blessedness.