Macbeth echoes the Witches in each of their first lines of the play: in Act I.i, the Witches end their first scene with the equivocation:
In Act I.iii, Macbeth's first lines are:
The day has been foul, in that he has been in bloody battle, unseeming traitors from the nave to chops;it has been a fair day, in that Scotland has won the battle. It will be a fair day when is named Thane of Cawdor, but it will be a foul day when he begins to plot Duncan's murder.
Killing the King is like killing God. It turns the natural order into chaos. Macbeth is actually below the Witches after he murders Duncan. He has effectively stopped time and the world from spinning. So, it is no wonder, when he wishes to finish a little prayer he overhears, he cannot. So says the "No Fear Shakespeare" translation:
But why couldn’t I say “Amen”? I desperately needed God’s blessing, but the word “Amen” stuck in my throat.
He will never again be granted God's blessing. He is an Anti-Christ, as he murders a just and innocent King. Later, he will murder his best friend, women, and children. The Witches do not directly kill anyone. Their petty vengeance against the sailor's wife is tame by comparison. They have the sailor drowned for chestnuts; Macbeth murders for the crown. Later, he will murder for murdering's sake: "blood will have blood."
Even though he is below the Witches, Macbeth will still command beautiful poetry. The Witches speak in the riddles of iambic tetrameter. Macbeth speaks in beautiful iambic pentameter, so he is above the Witches in language. The Witches speak in vague nouns; it is Macbeth that injects a moral/immoral argument in their riddles. So says critic Elaine Pilkington:
After Ross and Angus inform him that Duncan has bestowed upon him the title of the thane of Cawdor, validating the witches’ second title, Macbeth analyzes their words: “This supernatural soliciting / Cannot be ill, cannot be good. If ill, / Why hath it given me earnest of success / Commencing in a truth? I am thane of Cawdor. / If good, why do I yield to that suggestion / Whose horrid image doth unfix my hair / And make my seated heart knock at my ribs / Against the use of nature? (1.3.129 36). The witches’ words were neutral. It is Macbeth that puts a moral value to them, concluding that he must perform an unnatural act to acquire the title of king.
Macbeth, once natural, comes across the supernatural witches. After killing Duncan, Macbeth falls below them into the realm of the unnatural.
Here are a few more choice witchy morsels for you:
Stars, hide your fires;
Let not light see my black and deep desires:
The eye wink at the hand; yet let that be
Which the eye fears, when it is done, to see.
Ere the bat hath flown
His cloister'd flight; ere to black Hecate's summons
The shard-borne beetle with his drowsy hums
Hath rung night's yawning peal, there shall be done
A deed of dreadful note.
O, full of scorpions is my mind, dear wife!
Come, seeling night,
Scarf up the tender eye of pitiful day,
And with thy bloody and invisible hand
Cancel and tear to pieces that great bond
Which keeps me pale! Light thickens, and the crow
Makes wing to the rooky wood:
Good things of day begin to droop and drowse,
Whiles night's black agents to their preys do rouse.
For mine own good
All causes shall give way. I am in blood
Stepp'd in so far that, should I wade no more,
Returning were as tedious as go o'er.
Strange things I have in head that will to hand,
Which must be acted ere they may be scann'd.
It will have blood: they say blood will have blood.
Stones have been known to move and trees to speak;
Augures and understood relations have
By maggot pies and choughs and rooks brought forth
The secret'st man of blood.