mark 6:20 For Herod feared John, knowing that he was a just man and an holy, and observed him; and when he heard him, he did many things, and heard him gladly. - Free Bible Online

      20. For Herod feared John--but, as BENGEL notes, John feared not Herod.
      knowing that he was a just man and an holy--Compare the case of Elijah with Ahab, after the murder of Naboth (1Ki 21:20).
      and observed him--rather, as in the Margin, "kept" or "saved him"; that is, from the wicked designs of Herodias, who had been watching for some pretext to get Herod entangled and committed to despatch him.
      and when he heard him, he did many things--many good things under the influence of the Baptist on his conscience.
      and heard him gladly--a striking statement this, for which we are indebted to our graphic Evangelist alone, illustrating the working of contrary principles in the slaves of passion. But this only shows how far Herodias must have wrought upon him, as Jezebel upon Ahab, that he should at length agree to what his awakened conscience kept him long from executing.

JFB.