ISB ~ Galatians 4 v24

this is an allegory:An example of spiritual exegesis, which expounds the prophetic meaning of OT persons, places, events, and institutions in light of the New Covenant. Whereas literal exegesis interprets the words of the Bible, spiritual exegesis interprets the realities and events of the Bible described by its words (CCC 115-17).

• The author of Holy Scripture is God, who can signify his meaning, not only by words, as even man can do, but also by things. The first signification whereby words signify things belongs to the historical or literal sense. The signification whereby things signified by words also have their own signification is the spiritual sense, which is based on the literal and presupposes it (St. Thomas Aquinas, Summa Theologiae I, 1, 10).