St. Leo IX, 1049-1054

Godhead is co-essential and consubstantial, co-eternal and co-omnipotent, and of one will, power, and majesty; the creator of all creation, from whom all things, through whom all things, in whom all things [Rom. 11:36] which are in heaven or on earth, visible or invisible. Likewise I believe that each person in the Holy Trinity is the one true God, complete and perfect.

344. I believe also that the Son of God the Father, the Word of God, was born eternally before all time from the Father, consubstantial, co-omnipotent, and co-equal to the Father through all things in divinity; born of the Holy Spirit from the ever virgin Mary in time, with a rational soul, having two nativities, the one from the Father, eternal, the other from the Mother, in time; having two wills and operations, true God and true man, individual in each nature and perfect, not having suffered a fusion and division, not adopted or phantastical, the one and only God, the Son of God in two natures, but in the singleness of one person, incapable of suffering and immortal in divinity; but in humanity for us and for our salvation suffered in the true passion of the body and was buried, and arose from the dead on the third day in the true resurrection of the body; because of which we must declare with the disciples that He ate from no need of food but only from will and power; on the fortieth day after His resurrection with the flesh in which He arose, and with His soul He ascended into heaven and sits at the right hand of the Father, whence on the tenth day He sent the Holy Spirit, and thence, as He ascended, He will come to judge the living and the dead, and will render to each one according to his works.

345. I believe also that the Holy Spirit, complete and perfect and true God, proceeding from the Father and the Son, co-equal, co-essential, co-omnipotent and co-eternal with the Father and the Son in all respects, has spoken through the prophets.

346. That this holy and individual Trinity is not three Gods, but in three persons and in one nature or essence [is] one God omnipotent, external, invisible and incommutable, so I believe and confess, so that I may truly proclaim that the Father is not begotten, the Son is the only begotten one, and the Holy Spirit is neither begotten nor unbegotten, but proceeds from the Father and the Son.

347. (Variant Readings:) I believe that the one true Church is holy, Catholic and apostolic, in which is given one baptism and the true remission of all sins. I also believe in a true resurrection of this body, which now I bear, and in eternal life.

The articles of this creed almost agree with the questions which were customarily proposed according to the "Ancient statutes of the Church" [cf. n. 150 not.] to those to be consecrated bishops.—See the canon in ML 56, 879 B ff. [cf. also the Creed of Palaeologus n. 461 ff.].