The parable of the wedding feast closes off a series of parables that seem to be Jesus' answer to the question from religious leaders "By what authority are you doing these things and who gave you the authority?"
An excerpt of my sermon:
Now Jesus is not just telling these parables to continue his teaching which was interrupted by the challenge of the religious leaders. He is saying something while saying something else. In the first, Jesus tells the parable to show the challenge he presents to the rule of the religious leaders. Jesus tells them that their authority is disappearing because they are the second son who pays lip service to the father, but does not do his will. Tax collectors and prostitutes will enter the Kingdom before them because they have heard the invitation to repentance and obeyed. The religious leaders are afraid to even take a stand on where John’s baptism came from.
Read the whole thing here.
Listen to it: