From Saint John Chrysostom (around 345-407),
Bishop of Antioch, then of Constantinople, Doctor of the Church
Homilies on Saint Matthew, no. 64
“You too go along to my vineyard.”
"It is obvious that this parable is addressed both to people who have been virtuous since their youth and to people who become so only in their old age: to the former, to preserve them from pride and to stop them from reproaching the people of the eleventh hour; and to the latter, to teach them that they can deserve the same salary in a short time.
The Savior had just spoken about giving up wealth, about scorn for all goods, about virtues, which require a big heart and courage. For that, the zeal and energy of a youthful soul are necessary. So the Lord rekindles in them the flame of charity, strengthens their sentiments, and shows them that even those who came last receive the whole day’s salary.
All of Jesus’ parables - those about the virgins, the fishing net, the thorns, the barren tree – invite us to show our virtue in our actions. He speaks little about dogmas because they don’t require much effort. But he often speaks about life. Or rather, he talks about it all the time because, since life is a constant combat, the effort is also constant. "