The Two Sons
The second son, who personified the chief priests and Pharisees, responded to God’s call only with words, but did not fulfill that call in action. The first son, on the contrary, fulfilled the will of the father and went to work in the vineyard.
Jesus Christ: His Life and Teaching, Vol.4 - The Parables of Jesus, Metropolitan Hilarion Alfeyev
Matthew 21: 28 “But what do you think? A man had two sons, and he came to the first and said, ‘Son, go, work today in my vineyard.’ 29 He answered and said, ‘I will not,’ but afterward he regretted it and went. 30 Then he came to the second and said likewise. And he answered and said, ‘I go, sir,’ but he did not go. 31(a) Which of the two did the will of his father?”
They said to Him, “The first.”
Jesus said to them, “Assuredly, I say to you that tax collectors and harlots enter the kingdom of God before you. 32 For John came to you in the way of righteousness, and you did not believe him; but tax collectors and harlots believed him; and when you saw it, you did not afterward relent and believe him.
John called sinners to repent. Those who considered themselves sinners heeded the call. Those who feigned righteousness did not. Repentance, a change of mind, a desire to transform, or change. This is what the first son did: he repented, he changed his mind.
The term righteousness, in describing John the Baptist in this parable, occurs only a couple of times in Matthew outside of the Sermon on the Mount, and both times it occurs together with a mention of John the Baptist.
Righteousness describes the way that John the Baptist lived and the way in which every disciple of Jesus is called to walk.
In the Sermon on the Mount, righteousness is associated with the kingdom of heaven. Hence, it is not a superficial righteousness – the so-called righteousness of the Pharisees. it is radically different (as we saw when studying that Sermon).
The righteousness that Jesus preaches assumes a complete conformity between one’s inner and outer realities, between words and deeds.
Conclusion
In the parable, the one who acted is the one who did the will of the Father. Verbal assent is insufficient, and of no use if not followed by action. Yet, to act, even after not giving assent, is deemed as doing the Father’s will.
The accent is placed on action, on practice, not only on faith.
I often mused that, in the near future (measured by our distance from the darkness of the Great "Pandemic"), there would be a realignment of believing Christians based upon their reaction to the reaction of their institutional churches to the aforementioned event. This is not to disparage the importance of doctrine, for as an Orthodox Christian, it is something to which I deeply, unreservedly assent. But, let's face it, Christians today are more likely to be recognized as such for their behavior, than for their commitment, say, to the Chalcedonian affirmation. It is time, I think, to re-reflect upon "Mere Christianity" as explored in the writings of those concerned with Christian behavior, such as CS and those following him, the editors and contributors of Touchstone magazine, for example.