Act 4, Scene 3

Macduff and Malcolm speak together of Macbeth's treachery and try to find a way to overthrow him, and put Malcolm in his place. On page 186, Macduff refers to Macbeth’s jealousy and treachery as so: “this avarice sticks deeper: grows with more pernicious root than summer-seeming lust.” In essence, he is saying that Macbeth’s greed is deeply rooted, and that root is more harmful than youthful lust.
A group of people with a strange disease searched out King’s touch. Their disease is unmendable by the surgery of the time, and so they sought out the holy blessing of the King to cure them. The disease is called the King’s Evil, which is another allusion to strangeness and supernatural occurrences in Macbeth. The King is also said to have the holy ability of foresight. “The mere despair of surgery, he cures, hanging a golden stamp about their neck put on by holy prayers: and tis spoken, to the succeeding royalty he leave the healing benediction. With this strange virtue he hath a heavenly gift of prophecy, and sundry blessings hang about his throne that speak him full of grace.” Shakespeare did a clever thing my introducing the idea that Macbeth has holy power by virtue of the throne. HE is an unjust, fruitless, evil and false king, and so instead of being blessed with these powers the king is supposedly supposed to control, Macbeth has gone insane, and derives his insanity from the witches. The contrast is that the good king gets power from god, and the bad king becomes insane at the hand of witches.