Incarnation and theosis

Unique to  Christianity is its astounding concept that God has become man.

The incarnation or the enfleshment  is the concecpt that Christ  being  born of a virgin indicates his divinity, his being born of a woman shows his true humanity. According to the Council of Chalcedon (AD 451), Christ is fully human and fully divine. This union is sometimes called the hypostatic union.

As the early Church Fathers like Irenaeus (2nd c.) and Athanasius (4th c.) frequently said, God became man so that man might become divine.

Incarnation and theosis The Divinization of Humanity

 Because of the fact that divinity and humanity are united in the person of Christ, our humanity can now be united with God's divinity. We can share in the nature of the triune God.

So there's a two-way movement. God humbles himself, stooping downward to us, taking on our
nature, so that we can then be elevated, taking on his nature. The incarnation is the basis of our
divinization, but it is also the basis of the atonement. By taking on human flesh, Christ was able to pay thepenalty for the sin of all humanity through his death on the cross. Before being able to share in God's lifeand nature, humanity needed to be cleansed of sin. This cleansing is accomplished through Christ offeringhimself for our sins.

this article is adapted from Ortho-Wiki