An allusion is a reference, typically brief, to a person, place, thing, event, or other literary work with which the reader is presumably familiar. As a literary device, allusion allows a writer to compress a great deal of meaning and significance into a word or phrase. However, allusions are only effective to the extent that they are recognised and understood by the reader, and that they are properly inferred and interpreted by the reader. If an allusion is obscure or misunderstood, it can lose effectiveness by confusing the reader.
Some common allusions in frequent use nowadays include phrases like ‘If I’m not home by midnight, my car might turn into a pumpkin’ (a reference to the fairy story, ‘Cinderella’, where the heroine’s carriage to the ball is the result of a magic spell on a pumpkin, but where the magic only lasts until midnight) or speaking about a weakness as ‘my Achilles’ heel’ (alluding to the one weakness of Achilles in Classical mythology.) Such phrases are completely meaningless without the background story (Why should a car turn into a pumpkin? How can you have a heel belonging to someone else?), but are extremely evocative and effective if you know the things to which the phrase alludes. Allusion acts as a binding agent, giving people the pleasure of shared knowledge and unity, using language in a coded way that goes way beyond the surface meaning of words.
‘The day of the Lord’ is a phrase which features frequently in the Bible, to the extent that its New Testament usage relies heavily on allusion. To those soaked in the Scriptures, the phrase is shorthand for all kinds of things: judgment, destruction, darkness, God’s intervention in human history in ways that are nothing short of miraculous, the final righting of wrongs for which we all long. To fully understand what this phrase means (delving deeper into its meaning than saying ‘the Lord’s day’, meaning Sunday, would imply), we need the mindset of the prophets who were the main writers using this phrase, but we also need to see how the coming of Jesus and the victory He has won redefined and reshaped this phrase. Such a study is important, because the phrase is used so frequently in the Bible that it’s clearly important!