Mark now develops the theme of discipleship by means of another sandwich unit (6:6b–30), in which the mission of the Twelve (6:6b–13, 30) is divided by the poignant account of the martyrdom of John the Baptizer (6:14–29). The Greek word for “witness” is martyreō, from which the English word “martyr” is derived. By sandwiching the death of John between the sending and return of the Twelve, Mark signifies that those who heed Jesus’s summons to mission must be prepared for the ultimate witness of martyrdom.

Jesus “calls” and “sends” the disciples into mission in verse 7 with the same authority by which he himself ministers, and with which he commissioned them as apostles in 3:13–14. The sending into mission of disciples w…