1 John 5:9
Alleluia, alleluia. V. If we receive the testimony of men, the testimony of God is greater. Alleluia.
THE FORMULA CALLED “THE MERCIFUL TRINITY”
Of uncertain author and time; from Gaul about 500(?)
17 The merciful Trinity is one divine Godhead. Consequently the Father and the Son and the Holy Spirit are one source, one substance, one virtue, and one power. We say that God the Father and God the Son and God the Holy Spirit are not three gods, but we very piously confess one God. For although we name three persons, we publicly declare with the catholic and apostolic voice that they are one substance. Therefore the Father and the Son and the Holy Spirit, these three are one [cf. 1 John 5:7]. Three, neither confused, nor separated, but both distinctly joined, and, though joined, distinct; united in substance, but differentiated in name, joined in nature, distinct in person, equal in divinity, entirely similar in majesty, united in trinity, sharers in splendor. They are one in such a way, that we do not doubt that they are also three; and they are three in such a way that we acknowledge that they cannot be disjoined from one another. Therefore there is no doubt, that an insult to one is an affront to all, because the praise of one pertains to the glory of all.
18 ‘For this is the principal point of our faith according to the Gospel and the apostolic doctrine, that our Lord Jesus Christ and the Son of God are not separated from the Father either in the acknowledgment of honor, or in the power of virtue, or in the divine nature of substance, or by an interval of time.’ And therefore if anyone says that the Son of God, who just as he is truly God, so also is true man except in sin alone, ,did not possess something belonging to human nature or did not possess something belonging to the Godhead, he should be judged wicked and hostile to the Catholic and apostolic Church.