Summary: No matter the person or their history, Jesus is saying, "It's not too late for you or anyone else! There is more than enough room in God's purposes for everyone!" God makes no distinction, and we shouldn't either.
For six years when I was in junior high and high school, I tried out for the East Tennessee regional clinic band every year. For those of you who are not familiar with how these clinic bands work; they are put together through an audition process, and they consist of the "best" young instrumentalists in the region. The audition consists of a prepared piece, which the young players receive in advance and have time to practice. They also have to play some scales, which ones are determined in the audition room, and then they have to sight-read a piece of music. Based on the performance in each of those areas, every person who auditions is given a score, and then those instrumentalists receiving the top scores in each section are awarded with a "seat" in the band.
Needless to say, it's a great experience; an opportunity to play with some great young instrumentalists, to meet some new people, learn some new music, and to work with some fine conductors -- among other things. But the audition process is pretty rigorous for a young person. It doesn't matter if you are the top player at your school. It doesn't matter if you've been taking private lessons for years. It doesn't matter if you have the most expensive instrument out there. When you walk into that room to begin your audition, you are in the same boat as every other kid that has been in there that day, and every other kid that has yet to audition; everyone has an equal opportunity to make that band.
I'm sure that many of you have had similar experiences; maybe it was in sports, or on a test, or perhaps a job interview. There come times in our lives when we are put on par with everyone else, and it is a level playing field.
So it is, in a sense, in our scripture reading this morning. A handful of laborers have been working in the landowner's vineyard; some of them have worked all day, some of them half the day, and some of them only an hour. But when the time comes to pay the laborers, the playing field is leveled, and everyone gets paid equally; one denarius for twelve hours, one denarius for one hour. It seems so unfair, doesn't it? Today's Workers' Unions would have a field day with this one! "Why bother getting a full-time job when we can work quarter time or less and still get paid the same?" we wonder. This is very strange behavior exhibited by the landowner, and the manager just goes along with it.
But we have to remember that this is a parable, and Jesus' parables take real life examples that people can relate to and modify them a bit to teach us something about God and God's Kingdom. It doesn't take too much thinking to realize that in this parable, God is the landowner, Jesus is the manager, and we are the laborers. But that presents as many problems as it does solutions. We believe God to be a God of justice -- so why would God engage in such unjust behavior as to give equal reward for unequal work? Well, God is a just God, and there are parables to show that. But this parable isn't about God's justice. Much like the parable of the prodigal son, this parable is about God's grace, and God's grace puts us all on a level playing field.