18. For John had said unto Herod, It is not lawful for thee to have thy brother's wife--Noble fidelity! It was not lawful because Herod's wife and Herodias' husband were both living; and further, because the parties were within the forbidden degrees of consanguinity (see Le 20:21); Herodias being the daughter of Aristobulus, the brother of both Herod and Philip [JOSEPHUS, Antiquities, 18.5,4].

JFB.