double, double toil and trouble, fire burn and cauldron bubble
The witches are casting spells in a dark cave.
"Infected be the air whereon they ride,And damned all those that trust them! I did hear"
Macbeth wants to know the true meaning behind the prophecies. He demands that they tell him how to remain king.
Macbeth, Macduff has fled to England!
Three apparitions appear above Macbeth. One being an armed head, the second being a bloody child and the last being a crowned child. The head gives a warning to Macbeth to watch out for Macduff. The bloody child means "none of woman born shall harm Macbeth". and the last one is that he will never be overthrown until Dunsinane.
This quote is ironic because Macbeth is saying that anyone who trusts the witches is doomed. The irony is, Macbeth trusted the witches earlier in the play.
Lennox has just informed Macbeth that Macduff has fled to England. This makes Macbeth angry because he wasn't able to kill Macduff. This causes him to change his morals even more and kill Macduff's family. "Seize upon Fife, give to th’ edge o’ th’ sword His wife, his babes, and all unfortunate souls That trace him in his line."
Macduff is fleeing to England because he knows who Macbeth is turning into.