Act 3 - Nature

"Ay, in the catalogue ye go for men,

As hounds and greyhounds, mongrels, spaniels, curs,

Shoughs, water-rugs, and demi-wolves are clept

All by the name of dogs. The valued file

Distinguishes the swift, the slow, the subtle,

The housekeeper, the hunter, every one

According to the gift which bounteous nature

Hath in him closed, whereby he does receive

Particular addition, from the bill

That writes them all alike. And so of men." (Act 3, Scene 1, lines 93-101)

In this passage Macbeth talks about another kind of nature, the human nature. He says that you can classify each dog according to the natural gifts that separate it from all other dogs and that it’s the same with men.  

"But let the frame of things disjoint, both the worlds suffer,

Ere we will eat our meal in fear, and sleep

In the affliction of these terrible dreams

That shake us nightly." (Act3, Scene 2, lines 18-22)

Macbeth explains that the universe will fall apart, heaven and earth will crumble and he'll be having horrible dreams and eat in fear for what he has done.

 "Let it come down." (Act 3, scene 3, line 18)

The murderer replies to Banquo when he predicts that there will be rain, the murderer says then let it rain. Meaning "let it be" and let the rain down... of blood.

"Then comes my fit again. I had else been perfect,

Whole as the marble, founded as the rock,

As broad and general as the casing air.

But now I am cabined, cribbed, confined, bound in

To saucy doubts and fears." (Act 3, Scene 4, lines 22-26)

Macbeth says that he is scared again because they get Fleance go. Otherwise he would have been perfect, as solid as a piece of marble, as firm as a rock, as free as the air itself.