'Allegory' in the Bible

“Son of man, ask a riddle and tell a parable to the house of Israel,

Now these facts are about to be used [by me] as an allegory [that is, I will illustrate by using them]: for these women can represent two covenants: one [covenant originated] from Mount Sinai [where the Law was given] that bears children [destined] for slavery; she is Hagar.