The Gates Of Hell

Πύλας ᾅδου ὁ Θεῖοσ Λόγος ἐκάλεσε, τὰς τῶν ἀθέων τιμωρίας, τὰς τῶν αἱρέσεων βλασφημίας, αἶστισι πάσαις ἀνθεστῶσα ἡ τοῦ Θεοῦ Ἐκκλησία, τὰς μὲν καταγωνίζεται, ὑπὸ δὲ τῶν οὐ κατακοριεύεται. Ἅγιος Ἰσίδωρος Του Πηλουσιώτου, Βιβλίον Πρῶτον, Ἐπιστολή ΣΛΗ', Σερηνῳ Source: Migne PG 78.329b

The Divine Word calls the gates of hell those things which promote impiety, the blasphemies of heretics, all those unseen things which assail the Church of God, which it prevails against, for it shall never be ruled by such things. 1 Saint Isidore of Pelusium, Book 1, Letter 238, to Serenus 1 Mt 16.18