Mark 6:14–29
14 King Herod heard of it, for Jesus’ name had become known. Some said, “John the Baptist has been raised from the dead. That is why these miraculous powers are at work in him.” 15 But others said, “He is Elijah.” And others said, “He is a prophet, like one of the prophets of old.” 16 But when Herod heard of it, he said, “John, whom I beheaded, has been raised.” 17 For it was Herod who had sent and seized John and bound him in prison for the sake of Herodias, his brother Philip’s wife, because he had married her. 18 For John had been saying to Herod, “It is not lawful for you to have your brother’s wife.” 19 And Herodias had a grudge against him and wanted to put him to death. But she could not, 20 for Herod feared John, knowing that he was a righteous and holy man, and he kept him safe. When he heard him, he was greatly perplexed, and yet he heard him gladly.
21 But an opportunity came when Herod on his birthday gave a banquet for his nobles and military commanders and the leading men of Galilee. 22 For when Herodias’s daughter came in and danced, she pleased Herod and his guests. And the king said to the girl, “Ask me for whatever you wish, and I will give it to you.” 23 And he vowed to her, “Whatever you ask me, I will give you, up to half of my kingdom.” 24 And she went out and said to her mother, “For what should I ask?” And she said, “The head of John the Baptist.” 25 And she came in immediately with haste to the king and asked, saying, “I want you to give me at once the head of John the Baptist on a platter.” 26 And the king was exceedingly sorry, but because of his oaths and his guests he did not want to break his word to her. 27 And immediately the king sent an executioner with orders to bring John’s head. He went and beheaded him in the prison 28 and brought his head on a platter and gave it to the girl, and the girl gave it to her mother. 29 When his disciples heard of it, they came and took his body and laid it in a tomb.
30 The apostles returned to Jesus and told him all that they had done and taught.
This may be another one of Mark's sandwich techniques. He drops this story of John the Baptist in the middle of the story of the disciples being sent out and returning. If that is the case his main emphasis would then be on the up and down nature of God's Kingdom. It seems as if they are making great advances with the 12 being sent out. But in the midst of that there is a huge set back and great opposition.
Apart from the fascinating historical narrative (which is all attested to in Josephus's Antiquities book 18 chapter 6) and messed up family dynamics of royalty in the ancient world, this passage advances two main themes: Jesus' identity and the opposition narrative. First, this whole story is built around the question of Jesus' identity. The noted possibilities are Elijah, who was to return; a prophet like Isaiah, Jeremiah, or Ezekiel; and strangely, John the Baptist resurrected. Mark goes to great detail to describe Herod's paranoia around having John killed.
Note that even here, though people hold a high opinion of Jesus, nobody is saying that he is the Messiah. This again, is the main theme of the first part of this gospel—confusion and uncertainty as to the identity of Jesus. This is meant to take the reader along on this journey exploring who this guy really is. This tension will be resolved in chapter 8 when Peter finally definitively declares him to be the Christ and ultimately at his resurrection.
The second theme advanced here is the opposition narrative. The guy whom Jesus called the greatest man born to woman was, as one commentator said, "sacrificed to a cocktail wager." In the midst of a super encouraging advancement of the kingdom (Jesus empowering his disciples for mission) the reader is reminded of the grass roots movement and humble beginnings that the gospel community is at this point. This is a bitter pill to swallow. It is a reminder that the mission is linked to martyrdom; true discipleship may lead to death. If they treat John, and later Jesus, this way disciples must consider this and count the cost of following Jesus. As Jesus says in 8:34, "If anyone would come after me, he must deny himself, take up his cross and follow me." By the way, this statement immediately follows Peter's dramatic declaration of Jesus' true identity.