Book of Common Prayer (page 864)

Definition of the Union of the Divine
and Human Natures in the Person of Christ

Council of Chalcedon, 451 A.D., Act V

Therefore, following the holy fathers, we all with one accord teach men
to acknowledge one and the same Son, our Lord Jesus Christ, at once
complete in Godhead and complete in manhood, truly God and truly man,
consisting also of a reasonable soul and body; of one substance
(homoousios) with the Father as regards his Godhead, and at the same
time of one substance with us as regards his manhood; like us in all
respects, apart from sin; as regards his Godhead, begotten of the Father
before the ages, but yet as regards his manhood begotten, for us men and
for our salvation, of Mary the Virgin, the God-bearer (Theotokos); one
and the same Christ, Son, Lord, Only-begotten, recognized in two
natures, without confusion, without change, without division, without
separation; the distinction of natures being in no way annulled by the
union, but rather the characteristics of each nature being preserved and
coming together to form one person and subsistence, not as parted or
separated into two persons, but one and the same Son and Only-begotten
God the Word, Lord Jesus Christ; even as the prophets from earliest
times spoke of him, and our Lord Jesus Christ himself taught us, and the
creed of the Fathers has handed down to us.

Quicunque Vult

commonly called

The Creed of Saint Athanasius

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.

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.