Cassius tells Brutus to stab him. To be specific, he says, " There is my dagger,
And here my naked breast; within, a heart
Dearer than Plutus' mine, richer than gold:
If that thou be'st a Roman, take it forth;
I, that denied thee gold, will give my heart."
Cassius gives him the dagger and exposes his chest to be stabbed.