“Two natures of Jesus:
The two natures of Jesus refers to the doctrine that the one person Jesus Christ had/has two natures, divine and human. In theology this is called the doctrine of the hypostatic union, from the Greek word hypostasis (which came to mean substantive reality). Early church figures such as Athanasius used the term “hypostatic union” to describe the teaching that these two distinct natures (divine and human) co-existed substantively and in reality in the single person of Jesus Christ. The aim was to defend the doctrine that Jesus was simultaneously truly God and truly man.
Historical development:
The doctrine of the hypostatic union (the two natures of Jesus) was adopted as orthodox doctrine at the Council of Chalcedon in 451. Three major schools of theology were involved at the council: Alexandria, Antioch, and the West. The consensus of these three schools in the Chalcedonian Creed illustrates the catholicity (i.e. universality) of the ancient church. ^[1]^ The creed asserted two distinct natures, human and divine, and affirmed the one person of Jesus Christ.
Biblical basis:
One of the clearest passages in Scripture concerning the two natures of Jesus comes from John 1 (see on John 1). The Word (i.e. Jesus) “was with God, and the Word was God.” Moreover, the Word took on human flesh (John 1:14). Luke’s gospel also says that Jesus “increased in wisdom and in stature and in favor with God and man” (Luke 2:52).
The Communicatio Idiomatum:
“A doctrine that is related to the Hypostatic Union is the communicatio idiomatum (Latin for ‘communication of properties’). It is the teaching that the attributes of both the divine and human natures are ascribed to the one person of Jesus. This means that the man Jesus could lay claim to the glory He had with the Father before the world was made (John 17:5), claim that He descended from heaven, (John 3:13), and also claim omnipresence, (Matt. 28:20). All of these are divine qualities that are laid claim to by Jesus; therefore, the attributes of the divine properties were claimed by the person of Jesus.”[5]
God and man forever:
“Christ’s humanity was not a mere fleshly shell that God rented and used for a temporary amount of time. God did not just come to live in flesh as a man, but the ‘Word became flesh’ (John 1:14). God incorporated human nature into His eternal being. In the incarnation humanity has been permanently incorporated into the Godhead. God is now a man in addition to being God. At the virgin conception God acquired an identity He would retain for the rest of eternity. His human existence is both authentic and permanent. Jesus’ humanity is not something that can be discarded or dissolved back into the Godhead, but He will always and forever exist in heaven as a glorified man, albeit God at the same time.”^[6]^ Upon his ascension, Jesus was not deified, but rather was glorified.”
-Theopedia