Leaven And The Incarnation

Ζύμῃ ἡ Βασιλεία τῶν οὐρανῶν ἀφωμοίωται, τῇ τοῦ Κυρίου καὶ Σωτῆρος ἡμῶν ἀναμαρτήῳ σαρκώσει, ἀναφυρασάσῃ τὸν ἄπαντα κόσμον, καὶ ἑνὸς σώματος ὑποστάσει, ἐκ τῆς ἡμετέρας οὐσίας καὶ τῆς θεοτόκου Μαρίας ληφθέντος, τὴν ἀπ' αἰῶνος ἀνθρωπότητα εἰς παλιντοκίαν ἀνακαινισάσῃ.  Ἅγιος Ἰσίδωρος Του Πηλουσιώτου, Βιβλίον Πρῶτον, Ἐπιστολή ΣΑ', Διδυμῳ  Migne PG 78. 312

The kingdom of heaven is compared to leaven, 1 and this is the Incarnation of our Lord and Saviour without fault, mixing with the whole world, of one body, taken from our substance and from the God bearing Mary, that from eternity he might renew humanity to be born again. Saint Isidore of Pelusium, Book 1, Letter 201, to Didymus 1 Mt 13.33