Shakespeare used a variety of medieval and early modern literary sources in writing The Merchant of Venice. Scholars trace Portia’s three caskets to a thirteenth century collection of tales and anecdotes titled GestaRomanorum, which Chaucer is also believed to have used for source material. The bulk of the raw material for the plot of the play seems to come from Ser Giovanni Fiorentino’s Il Pecorone, a fourteenth century collection of stories which includes an episode about an Italian merchant who owes a pound of flesh to a Jewish moneylender after his godson courts a lady from Belmont using his borrowed cash. While the lady in Il Pecorone also dresses as a lawyer to defend the merchant in court and tricks the godson into giving her his ring, unlike Portia she’s a vengeful widow who drugs her lovers. Alexander Silvayn’s The Orator told a similar story of a Jew threatening to cut off a pound of Christian flesh, and some of Shakespeare’s language resembles Silvayn’s language.
Scholars often discuss Christopher Marlowe’s The Jew of Malta as a probable impetus and influence for The Merchant of Venice because it was first staged in London only a decade before Shakespeare wrote the play. While a lack of documentary evidence prevents us from knowing how involved the two playwrights were in each other’s lives and work, its safe to assume that Shakespeare would have at least heard about The Jew of Malta, if he hadn’t seen a production. In Marlowe’s play, Barabas, a Jewish merchant, goes on a vengeful killing spree that eventually includes his daughter, Abigail, after she converts to Christianity. Like The Merchant of Venice, The Jew of Malta has generated extensive debate about the text’s portrayal of Jews. Unlike Shylock, however, Barabas actually causes physical harm to other characters. The plays end differently as well, with Barabas finally caught in his villainy and killed while his enemies unite in their common hatred of him. The relatively gentle treatment of Shylock at the end of Merchant, in which Shylock is stripped of his money and religion but allowed to live, has caused some critics to speculate that Shakespeare intended Shylock as a humanistic response to Marlowe’s Barabas.