17 Herod was the one who had ordered the arrest of John, put him in chains, and sent him to prison at the nagging of Herodias, his brother Philip's wife. 18 For John had provoked Herod by naming his relationship with Herodias "adultery." 19 Herodias, smoldering with hate, wanted to kill him, but didn't dare 20 because Herod was in awe of John. Convinced that he was a holy man, he gave him special treatment. Whenever he listened to him he was miserable with guilt - and yet he couldn't stay away. Something in John kept pulling him back.
Matthew Henry's Commentary on Mark 6:17-20
Commentary on Mark 6:14-29
(Read Mark 6:14-29)
Herod feared John while he lived, and feared him still more when he was dead. Herod did many of those things which John in his preaching taught him; but it is not enough to do many things, we must have respect to all the commandments. Herod respected John, till he touched him in his Herodias. Thus many love good preaching, if it keep far away from their beloved sin. But it is better that sinners persecute ministers now for faithfulness, than curse them eternally for unfaithfulness. The ways of God are unsearchable; but we may be sure he never can be at a loss to repay his servants for what they endure or lose for his sake. Death could not come so as to surprise this holy man; and the triumph of the wicked was short.