Why dost thou whet thy knife so earnestly?

Gratiano
Why dost thou whet thy knife so earnestly?
Shylock
To cut the forfeiture from that bankrout there.
Gratiano
Not on thy sole but on thy soul, harsh Jew,
Thou mak'st thy knife keen. But no metal can,
No, not the hangman's axe, bear half the keenness
Of thy sharp envy. Can no prayers pierce thee?
Shylock
No, none that thou hast wit enough to make.
Gratiano
O, be thou damned, inexecrable dog,
And for thy life let justice be accused;
Thou almost mak'st me waver in my faith,
To hold opinion with Pythagoras
That souls of animals infuse themselves
Into the trunks of men. Thy currish spirit
Governed a wolf who, hanged for human slaughter,
Even from the gallows did his fell soul fleet,
And whilst thou layest in thy unhallowed dam,
Infused itself in thee, for thy desires
Are wolfish, bloody, starved, and ravenous.
Shylock
Till thou canst rail the seal from off my bond,
Thou but offend'st thy lungs to speak so loud.
Repair thy wit, good youth, or it will fall
To cureless ruin. I stand here for law.