Matthew 14:3-4

For Herod had John arrested and bound him and put him in prison [at the fortress of Machaerus, east of the Jordan, to keep him away] because of Herodias, the wife of his brother Philip, [Mark 6:17; Luke 3:19] for John had said to him, “It is not lawful (morally right) for you to have her [living with you as your wife].” [Lev 18:16; 20:21]