For Herod himself had sent forth and laid hold upon John, and bound him in prison for Herodias’ sake, his brother Philip’s wife: for he had married her.
Berean Study Bible (BSB) - Mark 6:17 >For Herod himself had ordered that John be arrested and bound and imprisoned, on account of his brother Philip’s wife Herodias, whom Herod had married.
Textus Receptus (TR) - Mark 6:17 >Αὐτὸς γὰρ ὁ Ἡρῴδης ἀποστείλας ἐκράτησε τὸν Ἰωάννην, καὶ ἔδησεν αὐτὸν ἐν τῇ φυλακῇ, διὰ Ἡρῳδιάδα τὴν γυναῖκα Φιλίππου τοῦ ἀδελφοῦ αὐτοῦ, ὅτι αὐτὴν ἐγάμησεν.