“Herod said

To his servants.

‘This is John the Baptist.

He has been raised

From the dead.

This is why these powers

Are at work in him.’

Herod had seized John.

He had bound him.

He had put him in prison,

On account of Herodias,

His brother Philip’s wife.”

καὶ εἶπεν τοῖς παισὶν αὐτοῦ Οὗτός ἐστιν Ἰωάνης ὁ Βαπτιστής· αὐτὸς ἠγέρθη ἀπὸ τῶν νεκρῶν, καὶ διὰ τοῦτο αἱ δυνάμεις ἐνεργοῦσιν ἐν αὐτῷ.

Ὁ γὰρ Ἡρῴδης κρατήσας τὸν Ἰωάνην ἔδησεν καὶ ἐν φυλακῇ ἀπέθετο διὰ Ἡρῳδιάδα τὴν γυναῖκα Φιλίππου τοῦ ἀδελφοῦ αὐτοῦ·

This mention of Herod and John the Baptist can be found in all 3 synoptic gospels, Mark, chapter 6:14 and 6:17, and Luke, chapter 9:7 and 3:19-20, and here.  As if this story was not complicated enough, Herod, the Roman ruler in Galilee, had already seized John the Baptist.  John had been complaining that Herod Antipas had married the wife of his half-brother Herod Boethus or Philip, after he had divorced his first wife, who went back to her father and started a war with Herod Antipas.  His new wife was called Herodias.  Thus, Herod Antipas said to his children or servants (καὶ εἶπεν τοῖς παισὶν αὐτοῦ) that he thought that Jesus was John the Baptist raised from the dead (Οὗτός ἐστιν Ἰωάνης ὁ Βαπτιστής· αὐτὸς ἠγέρθη ἀπὸ τῶν νεκρῶν).  How ironic since Jesus was to rise from the dead.  Herod thought the miraculous powers of John the Baptist were at work in Jesus (καὶ διὰ τοῦτο αἱ δυνάμεις ἐνεργοῦσιν ἐν αὐτῷ).  Herod knew that he had seized, bound, and, put John in jail (Ὁ γὰρ Ἡρῴδης κρατήσας τὸν Ἰωάνην ἔδησεν καὶ ἐν φυλακῇ ἀπέθετο).  In fact, he had him killed because of his new wife Herodias, who had been the wife of his brother Philip or Herod Boethus (διὰ Ἡρῳδιάδα τὴν γυναῖκα Φιλίππου τοῦ ἀδελφοῦ αὐτοῦ).