From His Most-incorrupt Mother, the Lord borrowed most-pure flesh, and to her, he granted Divinity in place of the flesh which she had given Him. Lord, such a most marvelous and most miraculous exchange.

St. Symeon the New Theologian

The Virgin-Mother is, as it were, the sole border connecting the created and the uncreated Divine Essence. And all who see God also recognize her has the place [containing] the Uncontainable. And all who lift up praise unto God also sing her praises after God. She is the reason for and blessing of those who came before her, and the gift and giver to those present and intercessor for those in eternity. She is the basis of prophets, beginning of apostles, confirmation of martyrs, and foundation of teachers. She is the glory of those on earth, joy of those in Heaven, adornment of all Creation. She is the beginning, the spring and root of hope prepared for us in the Heavens, the hope that we might all be vouchsafed by her prayers for us, to receive Jesus Christ our Lord, in glory Born of the Father before all ages, and latter days Incarnate of her.

St. Gregory Palamas

But just as the Son is given to us without a(n earthly) father, so, the Child is born without a carnal conception. Just as the Virgin did not know by what means she made up a body pleasing to God, she did not feel her birth-giving. As the prophets testified, Her birth-giving was without travail: “before her pain came, she was delivered of a man child.” (Isaiah: 66: 7).

Holy Hierarch Gregory of Nyssa