Why does Antony tell the crowd that he does not plan to read Caesar's will to them?
As Cassius recognizes in urging that he be killed, Mark Antony is a highly skilled orator and is not shy about using rhetorical tricks to whet the appetite of the crowd. His announcement in Act III, Scene 2, that he does not plan to read Caesar's will to the assembled commoners is designed to create a demand that he do precisely that, read the will.
Antony begins this part of his speech by telling the crowd, which has just heard Brutus' justification, what a wonderful document it is that he does not plan to read,
But here's a parchment with the seal of Caesar;
I found it in his closet, 'tis his will.
Let but the commons hear this testament—
Which, pardon me, I do not mean to read—
And they would go and kiss dead Caesar's wounds
And dip their napkins in his sacred blood,
Yea, beg a hair of him for memory,
And, dying, mention it within their wills,
Bequeathing it as a rich legacy
Unto their issue.
When the crowd demands he read the will, Antony hesistates again, allowing the pressure to build up, but in the process he "accidentally" tells them more detail about its contents:
'Tis good you know not that you are his heirs,
For if you should, O, what would come of it!
Anthony then cleverly brings the conspirators back into the picture, so that the crowd turns on them in wrath:
The predictable result is a burst of hostility against the conspirators, so strong that Anthony, speaking now literally over Caesar's corpse, is soon able to refer to them as "traitors":
This was the most unkindest cut of all;
For when the noble Caesar saw him stab,
Ingratitude, more strong than traitors' arms,
Quite vanquish'd him.
The crowd has now turned into a lynch mob, but Anthony, playing on their emotions to the limit, makes a great show of holding them back one last time:
Good friends, sweet friends, let me not stir you up
To such a sudden flood of mutiny.
They that have done this deed are honorable.
Then, after further inflaming them with more material from the will, he sends the mob off, satisfied with his work:
Now let it work. Mischief, thou art afoot,
Take thou what course thou wilt.