23 This sublime doctrine, which is drawn from the gospels and differs in no way from that of the council of Ephesus refutes Eutyches as well as Nestorius. The dogmatic definition of the council of Chalcedon concords with it absolutely and perfectly, for this definition likewise defines two distinct natures and one person in Christ in the following clear and precise words: 'This great and holy oecumenical council condemns those who pretend that there were two natures in the Lord before the union, and imagine that there was only one after the union. Following, therefore, in the traditions of the holy Fathers we teach that all with one voice confess that the Son [of God] and our Lord Jesus Christ are one and the same, and that he is perfect in his divinity, perfect in his humanity, true God and true man, made of a rational soul and a body, consubstantial with the Father in his divinity, and the same also in his humanity received from the Virgin Mary in recent times for our sake and for our salvation, one and the same Christ, the Son, the Lord, the Only Begotten, having two natures without confusion, change, division or separation; the distinction between the natures was not removed by the union, but the properties of each remain inviolate and are joined together in one person. He is not sundered or divided into two persons, but is one and the same Son and only Begotten God the Word, the Lord, Jesus Christ' (Mansi. vii, 114 and 115).
Source: Sempiternus Rex Christus (Vatican.va)