Mark telleth us, Mark 6:20, that Herod feared, that is, reverenced and respected, John, knowing that he was a just man and an holy, and observed him; and when he heard him, he did many things, and heard him gladly. John was very popular, and all men counted him as a prophet; so that probably Herod sent for him to the court, and heard him there. John seeing Herod live in adultery and incest, was not able to suffer such a sin upon him, but tells him he did that which was not lawful for him to do, for God's law had forbidden such marriages. Mark addeth, that Herodias also had a quarrel against him, and would have killed him; but she could not, because of the respect which Herod had for him. But this wore off, for Matthew tells us... \see Matthew 14:5\
Related Commentaries of Matthew 14:4
Matthew 14:4
4 For John said unto him, It is not lawful for thee to have her.