Verses 18, 19. - For John said unto Herod. The Greek tense (ἔλεγε) implies more than the simple expression, "he said;" it implies a repeated warning. We learn from St. Matthew (Matthew 14:5) that Herod would have killed John before, but he feared the people. Here St. Mark says that Herodias set herself against him, and desired to kill him; and she could not; for Herod feared John. There is no contradiction between the two evangelists. The case appears to have been this: that at first Herod desired to put John to death, because John had reproved him on account of Herodias. But by degrees John gained an influence over Herod by the force of his character, and by his holy life and teaching.

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.For John had said unto Herod,.... He had been personally with him, and had plainly and freely told him of his sin, and faithfully reproved him for it; alleging what he had done was contrary to the law of God:

it is not lawful, for thee to have thy brother's wife: See Gill on Matthew 14:4.