“For John said unto him, It is not lawful for thee to have her.”
King James Version (KJV)
14:4 It is not lawful for thee to have her - It was not lawful indeed for either of them to have her. For her father Aristobulus was their own brother. John's words were rough, like his raiment. He would not break the force of truth by using soft words, even to a king.
Mt 14:4 It is not lawful for thee to have her. The marriage was unlawful for these three reasons: (1) The former husband of Herodias (Philip) was still living. (2) The former wife of Antipas was still living. (3) Besides, the Jewish law did not permit a man to marry his niece.