Book of Jonah
The allegory of the Aspidochelone borrows from the account of whales in Saint Isidore of Seville's "Etymologiae". Isidore cites the prophet Jonah; the Vulgate translation of the Book of Jonah translates Jonah 2:2 as "Exaudivit me de ventre inferni": "He (the Lord) heard me from the belly of Hell". He concludes that such whales must have bodies as large as mountains.