“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.”
King James Version (KJV)
6:15 A prophet, as one of the prophets - Not inferior to one of the ancient prophets.
6:16 But Herod hearing thereof - Of their various judgments concerning him, still said, It is John.
Mr 6:17 For the Herodias' sake. This states why John was cast into prison, on account of the instigation of the adulterous woman, a fact omitted by Matthew.