For John had said unto Herod, It is not lawful for thee to have thy brother's wife.
For John had said unto Herod,.... He had been personally with him, and had plainly and freely told him of his sin, and faithfully reproved him for it; alleging what he had done was contrary to the law of God:
It is not lawful, for thee to have thy brother's wife:
See Gill on "Matthew 14:4".