This parable offers us a lot of lessons (Today's Mass Reading - Matthew 20:1-16).
First, it teaches us to be charitable. Slaves and servants are better off because they can eat with or after their masters. But day laborers only get to eat when they earn from a day’s work. Their presence in the marketplace, still searching for work at the final hour of day, reflects desperation. So even if it would mean that the household owner would be in the losing end, he still hired them. What matters for the household owner was that the jobless have something to get by for the day.
Second, it teaches us to be humble. The household owner represents God and the workers are the beneficiaries of God’s benevolence. In the end, it is not about what we think we deserve but what God thinks we deserve. If we are to understand how the workers who came early in the day reacted, we will see that their minds were operating on the premise that they have done much and therefore should be paid as much. But we have to accept the fact that, as creatures of God, we are just at the receiving end. We need to be humble in accepting what God would deem fit for us.
Next, it teaches us to be more accepting of others, especially those who came much later than we do. This clearly speaks to the old-timers who act as if they own the church, who develop pride simply because they were the pioneers and as such have the right to everything. It also teaches us how to understand and value the work that we do for God. The first group worked because they knew that they would be given the compensation agreed upon. The workers who were invited last didn’t have to agree to anything. They just worked and left their fate to the household owner. This tells us that, in the end, it is not the work that we do for God that matters but what motivates us. Do we serve Him because we know we will be justly compensated in the end?