Mark 6:18-19

6:18 For John had repeatedly told Herod, “It is not lawful for you to have your brother’s wife.” 6:19 So Herodias nursed a grudge against him and wanted to kill him. But she could not

Mark 6:27

6:27 So the king sent an executioner at once to bring John’s head, and he went and beheaded John in prison.