In act 2, scene 6 of Shakespeare's The Merchant of Venice, Shylock's daughter, Jessica, elopes with Lorenzo, a penniless Christian. By act 2, scene 8, Shylock has roused the Duke and importuned him to search Bassanio's ship. Shylock believes that Jessica and Lorenzo are hiding there, but they are nowhere to be found.
Solanio mocks Shylock to Salarino, who remarks that all the young boys in Venice are making fun of Shylock in the streets.
SALANIO. I never heard a passion so confus'd, / So strange, outrageous, and so variable, / As the dog Jew did utter in the streets: / My daughter!—O my ducats!—O my daughter! / Fled with a Christian?—O my Christian ducats!— / Justice! the law! my ducats, and my daughter! / A sealed bag, two sealed bags of ducats, / Of double ducats, stol'n from me by my daughter! / And jewels; two stones, two rich and precious stones,
Stol'n by my daughter!—Justice! find the girl! / She hath the stones upon her, and the ducats!
SALARINO. Why, all the boys in Venice follow him / Crying,—‘His stones, his daughter, and his ducats.’ (2.8.12-24)
Already resentful of how he's treated by Christians on a day-to-day basis, Shylock now has even more reason to hate Christians because his daughter eloped with Lorenzo.
At the beginning of act 3, scene 1, Shylock hears the news on the Rialto that Antonio's ships have faltered at sea, and that Antonio might not be able to pay back the loan that he begged Shylock to give him.
The irony of the situation is not lost on Shylock.
SHYLOCK. There I have another bad match: a bankrupt, / a prodigal, who dare scarce show his head on / the Rialto; a beggar, that was used to come so smug / upon the mart. (3.1.38-40)
Shylock takes the opportunity to mock Antonio, calling him a "bankrupt" and a "prodigal." Shylock ridicules Antonio for being a "beggar" because he's lost his ships at sea, when just a short time ago Antonio looked down on Shylock. Shylock is no doubt reminded again of all the times Antonio cursed him, and called him a “misbeliever" and a "cut-throat, dog," and spat on him for being a Jew. (1.3.110-111)
SHYLOCK. Let him look to his bond: he was / wont to call me usurer;—let him look to his bond: he / was wont to lend money for a Christian courtesy;—let / him look to his bond. (3.1.40-43)
The tables have turned. The abused and downtrodden Shylock, the Jew, now has the upper hand against Antonio, a Christian. Shylock intends to take revenge against Antonio for the way he's been treated by the man, and more widely, by the entire Christian community.
As effecting and compelling as these lines are to the audience in terms of giving the audience a sense of what Shylock feels at this moment, what follows in the scene is even more compelling.
"He hath disgraced me," Shylock says about Antonio. "[A]nd what's his reason?" Shylock asks. (3.1.47-50)
Shylock answers his own question with one of the most famous and compelling speeches in all of Shakespeare's plays.
SHYLOCK. ...I am a Jew: hath not / a Jew eyes? Hath not a Jew hands, organs, dimensions, / senses, affections, passions? Fed with the / same food, hurt with the same weapons, subject to / the same diseases, healed by the same means, / warmed and cooled by the same winter and summer, / as a Christian is? If you prick us, do we not / bleed? if you tickle us, do we not laugh? If you / poison us, do we not die? and if you wrong us, shall / we not revenge? If we are like you in the rest, we will / resemble you in that. If a Jew wrong a Christian, / what is his humility? Revenge. If a Christian wrong / a Jew, what should his sufferance be by Christian / example? Why, revenge! The villainy you teach me I / will execute; and it shall go hard but I will better the / instruction. (3.1.50-64)
Shylock intends to teach Antonio a hard lesson, but it remains to be seen on whose head the hardest lesson falls.