Matthew 14:4

‘For John said to him, “It is not lawful for you to have her.” '

Thus John had boldly approached Herod and told him that what he was doing was against the Law of God. Herod's immediate response had been to imprison him. ‘John said to him continually' (imperfect tense) that what he was doing was ‘unlawful' (against the Law of God). The continual charge of doing what ‘was not lawful' would have aroused fears in Herod that John was planning an insurrection against him, especially in view of John's increasing popularity and his fierce declarations of judgment. Like his father he was no doubt somewhat paranoid.