Have you ever noticed that at the centre of a parable the main character often says something to themselves?* This feature of parables is known as a soliloquy – it’s a dramatic device also used by playwrights such as Shakespeare.
The importance of this device is that it reveals the motives of those involved in a parable: it tells us why the prodigal son decided to go home, or why his brother took exception to the celebration held on his return. Because the Bible uses parables as a teaching device, these internal monologues should either guide our own motives or display to us something of God’s.
For example, in Luke 16:3-4 the steward is coming to terms with the fact that he will soon be out of employment and have no means of living. It is this moment of realisation that spurs him into action, and holds the key to what is an otherwise difficult parable: we are to use what we have, in the time that we have, with a focus on our eternal future (as in Eph. 5:15-16). There’s a short explanation in this article: ‘What is the meaning of the parable of the unjust steward in Luke 16?’.
While Matthew 20:8 is not strictly a soliloquy, it takes its place in the centre of the parable and it’s the understanding of this remark that holds the meaning of the parable, so we can treat it as such. Why would the employer pay the last group of workers first? So that those hired first may also see his generosity, but also understand the just nature of their employer, and perhaps to cause them to consider the dedication of those who had waited over eight hours that day to gain employment.
You may not find a similar remark in every parable, but when you do, I would urge you to give it your full consideration – it may well be the reason for the conclusion given after the parable is finished.
* If you haven’t, perhaps you’d like to read Luke 15:17-19 & 29-30, 16:3-4, 20:13 and Matthew 20:8 to see some examples.