John Is Rejected By Herod (3:19-20).
‘But Herod the tetrarch, being reproved by him for Herodias his brother's wife, and for all the evil things which Herod had done, added this also to them all, that he shut up John in prison.'
Finally we come to the last verse in the chiasmus which parallels the opening verse (Luke 3:1). Here we discover what those great rulers can do. The word was always surrounded on all sides by powerful people who would seek to suppress it. We have had such people listed in Luke 3:1, and now the first of them will begin his evil work, later to be followed by the High Priest and then Pilate. But here Herod, whom John reproved because he openly sinned by taking his brother's wife Herodias, and for many other wrong things that he did, added to his crimes by shutting John up in prison. So does John's ministry come to an end, although not its influence, for his brave disciples will visit him in prison and pass on his message.
Herod's sin was a gross one. He had seduced the wife of his brother and stolen her from him, both forbidden under Jewish law (Leviticus 18:16; Leviticus 20:21). It was, of course adultery at the same time. Both he and Herodias left previous marriages in order to marry each other. Since Herodias had been married to Herod's half-brother, Herod Philip, and was the granddaughter of Herod's father and daughter of another half-brother of Herod, she was in effect Herod's wife, sister-in-law and niece all at the same time.
But it must have seemed to many in the outside world as though, in the death of John, the wonderful career of a blazing star had come abruptly to an end. It boded ill for the future. It seemed clear that in this Roman world prophets did not last long. It looked as though the world's authorities had won again and that God's work had been effectively extinguished. But what none realised was that he had lit a touch paper that would cause an explosion which would reach to the ends of the world (Acts 1:8). And Luke's purpose in mentioning this here is so that John can now be left behind because the brighter star has arisen. John's work has been accomplished and eventually he will go to his rest. Yet it is also a forewarning of what will happen in the future. The rulers of this world did not welcome the prophet of the Most High, how much less will they welcome His Son. So John's ministry provides a brief summary and warning of what the career of Jesus will also be like from start to finish.
However, there is also another aspect to this. Luke wants any non-Christian reader to see that Christianity revealed itself as subject to those who were in authority over them, and that in general those authorities approved of them. Herod was an exception here for personal reasons. But even he will eventually be glad to see Jesus and will eventually send Him back to Pilate without laying any charge against Him (Luke 23:6-12). Meanwhile it has been made clear that Jesus has rejected any temptation to take over world-rulership.