In Act 4, scene 1, the three witches circle around the cauldron to chant spells and add bizarre ingredients to the cauldron, which the goddess of witchcraft, Hecate, compliments them on.
Oh well done! I commend your pains, and every one shall share i' th' gains.
Double, double toil and trouble. Fire burn, and cauldron bubble.
Macbeth then arrives and asks the witches to tell him about the prophecies. The witches show him three apparitions. The first apparition is of a head with an armor telling him to "beware Macduff." The second is of a bloody child telling him no man born of a woman shall harm him. Then a crowned child holding a tree appears which tells him he's safe until Birnam Wood moves to Dunsinane Hill.
After the witches vanish, Lennox arrives to tell Macbeth the news of Macduff leaving to England. Macbeth orders the murderers to get into Macduff's castle and kill his wife and children.
Macduff is fled to England.
The castle of Macduff I will surprise, seize upon Fife, give to th' edge o' th' sword, his wife and his babes
In scene 2, a messenger hurries in to warn Lady Macduff that she is in danger but it was too late. She had no time to escape before the murderers enter Macduff's castle and kill his son and wife.
I doubt some danger does approach you nearly.
In scene 3, Malcolm tests out whether Macduff's trustworthy or not. He decides to go on about when he becomes a king he'll be far worse than Macbeth. He claims he's very violent and greedy. After Macduff disagrees with his future king and proves his loyalty, Malcolm explains his lies and embraces him as an ally.
To make me hunger more, that I should forge, quarrels unjust against the good and loyal, destroying them for wealth.
All these are portable, with other graces weighed.
After Ross enters, Malcolm reveals that he will return with ten thousand soldiers lent him by the English king. Ross then confesses to Macduff about the death of his wife and children. Macduff is absolutely devastated and crushed with grief but Malcolm tells him to turn his grief into anger and revenge Macbeth.
Your castle is surprised, your wife and babes, savagely slaughtered.
Gracious England hath, lent us good Siward and ten thousand men.
Be this the whetstone of your sword. Let grief convert to anger.