He took our flesh and our flesh became God, since it is united with God and forms a single entity with him. For the higher perfection dominated, resulting in my becoming God as fully as he became man.
Gregory of NazianzusMore Gregory of Nazianzus quotes
If anyone does not believe that Holy Mary is the Mother of God, he is severed from the Godhead. If anyone should assert that He passed through the Virgin as through a channel, and was not at once divinely and humanly formed in her (divinely, because without the intervention of a man; humanly, because in accordance with the laws of gestation), he is in like manner godless.
Gregory of Nazianzus