CLAUDIO: Death is a fearful thing.
ISABELLA: And shamed life a hateful.
CLAUDIO: Ay, but to die, and go we know not where;
To lie in cold obstruction and to rot;
This sensible warm motion to become
A kneaded clod; and the delighted spirit
To bathe in fiery floods, or to reside
In thrilling region of thick-ribbed ice;
To be imprison'd in the viewless winds,
And blown with restless violence round about
The pendent world; or to be worse than worst
Of those that lawless and incertain thought
Imagine howling: 'tis too horrible!
The weariest and most loathed worldly life
That age, ache, penury and imprisonment
Can lay on nature is a paradise
To what we fear of death.
Isabella replies, "Alas, alas!" This is the precise moment, I think, depicted in the painting. Isabella sympathetically lays her hands upon her brother's heart to comfort him and looks up at him with obvious pity and concern. But Claudio looks away with furrowed brow and awkwardly fiddles with the shackles on his leg. He knows that what he is to say next must be put in the most diplomatic terms, for he is going to ask her to trade her virginity for his life. Now the scene makes sense: Isabella's expression, Claudio's awkwardness, the half-open mouth prepared to ask for this sacrifice, and his gaze directed away from sister, whom he cannot look in the eye as he asks of her what he must.
CLAUDIO: Sweet sister, let me live:
What sin you do to save a brother's life,
Nature dispenses with the deed so far
That it becomes a virtue.
ISABELLA: O you beast!
O faithless coward! O dishonest wretch!
Wilt thou be made a man out of my vice?
Is't not a kind of incest, to take life
From thine own sister's shame? What should I think?
Heaven shield my mother play'd my father fair!
For such a warped slip of wilderness
Ne'er issued from his blood. Take my defiance!
Die, perish! Might but my bending down
Reprieve thee from thy fate, it should proceed:
I'll pray a thousand prayers for thy death,
No word to save thee.
CLAUDIO: Nay, hear me, Isabel.
ISABELLA: O, fie, fie, fie!
Thy sin's not accidental, but a trade.
Mercy to thee would prove itself a bawd:
'Tis best thou diest quickly.
CLAUDIO: O hear me, Isabella!