Explain Macbeth's reasons for not killing Duncan using direct quotes ?

One reason why he doesn't kill him is because Macbeth is "his kinsman". Also because Macbeth is "his subject". Since Macbeth is "his host" he really should "against his murderer shut the door," not "bear the knife" himself. Duncan "hath been so clear in his great office," that it would be bad to kill such a great king.