“For John had said unto Herod, It is not lawful for thee to have thy brother’s wife.”
Mark 6:18 — Greek Interlinear
Church Fathers on Mark 6:18
The Evangelist Mark, taking occasion from what went before, here relates the death of the Forerunner, saying, 'For Herod himself had sent forth and laid hold upon John, and bound him in prison for Herodias' sake, his brother Philip’s wife: for he had married her.'
Ancient history relates, that Philip, the son of Herod the great, under whom the Lord fled into Egypt, the brother of this Herod, under whom Christ suffered, married Herodias, the daughter of king Aretas; but afterwards, that his father-in-law, after certain disagreements had arisen with his son-in-law, had taken his daughter away, and, to the grief of her former husband, had given her in marriage to his enemy; therefore John the Baptist rebukes Herod and Herodias for…
Or else, the head of the law, which is Christ, is cut off from His own body, that is, the Jewish people, and is given to a Gentile damsel, that is, the Roman Church, and the damsel gives it to her adulterous mother, that is, to the synagogue, who in the end will believe. The body of John is buried, his head is put in a dish; thus the human Letter is covered over, the Spirit is honoured, and received on the altar.