For John had said unto Herod, It is not lawful for thee to have thy brother’s wife.
Berean Study Bible (BSB) - Mark 6:18 >For John had been telling Herod, “It is not lawful for you to have your brother’s wife!”
Textus Receptus (TR) - Mark 6:18 >Ἔλεγε γὰρ ὁ Ἰωάννης τῷ Ἡρῴδῃ ὅτι Οὐκ ἔξεστί σοι ἔχειν τὴν γυναῖκα τοῦ ἀδελφοῦ σου.