Homily 108 — as quoted by Pitre (p 137)
The miraculous birth of Jesus from Mary's womb is a 'mystery' that is ultimately 'above the capacity of our intelligence and our words.'
No freely usable English translation of this passage is online, so the note keeps Pitre's quotation and links to the full text. Translation: as quoted by Pitre (via Gambero).
In Jewish Roots of Mary
Why it is cited
The miraculous birth is a mystery 'above the capacity of our intelligence and our words' — Severus, cited by Pitre beside Ephrem.