After happening upon the bloodied corpse of Duncan lying in his bed, Macduff exclaims to his companions:
Most sacrilegious Murder hath broke ope
The Lord's anointed temple and stole thence
The life o’ the building.
He thus compares the body of the King to a holy temple (like, for example, the Temple in Jerusalem) that has been broken by his murder. It was a belief common in Shakespeare's day--indeed one espoused by the reigning king of England, James I--that monarchs were the chosen representatives of God on Earth. They ruled, in short, by divine right, and folk traditions in a number of different European kingdoms even held that the touch of a King had healing powers. So Duncan was "anointed" by God, and his body was thus sacred. His murder was not just treason or a political assassination, it was, as Macduff says, sacrilege. This metaphor underscores the horror of the deed, as does Macduff's description of the scene as a "new Gorgon" that will destroy the sight of anyone who sees it. Medusa, in Greek mythology, was a Gorgon, and looking at her face turned one to stone. But the King as a sort of anointed figure would have especially resonated with Shakespeare's audiences.