Fiat of God, fiat of Mary

"In the days of the creation of the world, when God was uttering His living and mighty 'Let there be', the word of the Creator brought creatures into the world.  But on that day, unexampled in the life of the world, when Divine Miriam uttered Her brief and obedient 'So be it', I hardly dare to say what happened then—the word of the creature brought the Creator down into the world."

     Philaret (LC:  Filaret) Drozdov, Metropolitan of Moscow (1782-1867), Sermon 23 on the Annunciation (1823), as quoted by Leonid Ouspensky on p. 172 of Leonid Ouspensky and Vladimir Lossky, The meaning of icons, trans. G. E. H. Palmer & E. Kadloubovsky (Crestwood, NY:  St. Vladimir's Seminary Press, 1982).  Fiat is the term in the Vulgate of Gen 1 (cf. Γενηθήτω), just as in the Vulgate of Lk 1:38 (cf. γένοιτό).  Since I don't have ready access to a modern printed edition of the Слова и речи (Slova i rechi), and haven't yet located it in the 19th-century printings that have been scanned into repositories like the Hathi Trust Digital Library, I'll have to trust for now the text of this sermon available here, and hope I've selected the right words exactly:

Во дни творения мира, когда Бог изрекал Свое живое и мощное: «да будет», слово Творца производило в мир твари: но в сей безпримерный в бытии мира день, когда Божественная Мариам изрекла свое кроткое и послушное «буди», – едва дерзаю выговорить, что тогда соделалось, – слово твари низводит в мир Творца.

     My thanks to Dr. Richard B. Steele for quoting this in English originally.