The servant goes at the 11th hour and hires the men who others had refused, presumably because they didn't look strong enough for the work. And they get paid the very same wage as those who had worked all day. This element of unreality serves to highlight the (humanly) irrational zeal of the Lord for the spread of the Gospel in the last days before His return. He will take on anyone who is willing to work, no matter how feebly, no matter for how short a time; the fact they are standing there ready and willing to do their little bit is what is important to Him. A man does not usually go out between 4 and 5 p.m. looking for more labourers, with sunset approaching. He must have had an unusually great need for workers, racing against time to get the harvest in. And this is the very urgency of the Gospel, and the passion of the Lord's desire to get the harvest reaped. God could reap the harvest of the earth, requiring not help from man. But He has chosen to work through men in the preaching of the Gospel, and therefore the number of workers and their zeal reflects the amount of harvest of souls that can be reaped. The eternal destiny of others is therefore seen to depend on our extent of labour in preaching. It’s also apparent that the amount of harvest was unreally huge- hence the unusual running backwards and forwards to get more workers. One expects the manager to know the size of the harvest and hire the right number of labourers at the start of the day. But in this parable, he doesn’t. The awesome size of the potential harvest out there in this world means that never should we conclude that ‘nobody’s interested’. There is a huge harvest out there. And in passing, it can be noted that grapes have to be harvested at just the right time. If they’re left even a day too long on the vine, the sugar content becomes too high and they are no use. We can perhaps infer that the parable describes a scene on a Friday, with the Sabbath coming on when nobody can work- and yet it is just the right day for reaping the harvest. This makes the obvious connection in our minds- that just before the Sabbath day of the Millennium, in the last days, there is an abnormally huge harvest to be reaped. And this would connect with other Biblical teaching about a great appeal being made to all nations, just prior to the Lord’s return.
The parable also yields the lesson that those men would not normally work for one hour. We are to imagine those men with families at home who needed feeding. No pay that day, no food. But they were willing to do at least something. And their generous Lord simply pitied their poverty, so he gave them a day's wage- even to the 11th hour workers. And this is the Lord who has graciously hired us. Likewise, no rich King who finds that the wedding of his son will be poorly attended would go out and invite beggars. The element of unreality is that he so wants every place filled. No human King, nor his son, would want riff raff at the wedding, just because his own class of people turned down the invitations. But the King of Heaven is unlike any human king. He wants others to share in the joy of His Son, and absolutely nobody is too low to share; and moreover, He has a compelling desire to fill those places. The implication is that the net is being spread wider and more compulsively as the days shorten unto the supper.
No employer really pays all workers the same amount as the 11th hour worker; no creditor would really cancel debts simply because the debtors can’t afford to pay, and take nothing at all from them; no father would really give preferential treatment to a wayward son over a son who had never disobeyed him. But the point is, God acts in the very opposite way to how we do or would do. His grace to sinners makes no human sense. And He asks us through these parables of His Son to walk out against the wind and follow His example in our treatment of sinners. Our own natural sense cries out that he who works most should have the most pay; but the unreality of the parable teaches us that this principle is set aside in the way God deals with us. Any gift from the Father and Son is by grace alone. The elements of unreality in the parables often bring out the extent of God’s grace. The fruit farmer [=God] asked His worker [= the Lord Jesus] to cut down a barren fig tree. But this worker had such fondness for the tree, he was so unusually concerned for it, that he pleaded that it be given some more time. This reflected the Lord’s love for Israel, a love beyond all reason. Likewise, which wealthy person would ever arrange a banquet and invite the very dregs of society to it? Here is the Father’s amazing grace. Sometimes we have to fill in the details [another feature of the Lord’s amazing stories] in order to perceive this grace. The younger son, for example, demanded his share of the inheritance; and thus he lost his name, forfeited any claim to family membership, and openly showed that he did not wish to be part of his father’s family. And yet he was received back with such grace and longing by the Father.