There is One God and One Mediator between God and man, the man Jesus Christ (cf. I Tim. 2:5). For He still pleads even now as man for my salvation; for He continues to wear the Body which He assumed, until He make me a god by the power of His Incarnation; although He is no longer known after the flesh (cf. II Cor. 5:16) ? I mean, the passions of the flesh, the same, except sin, as ours.
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