Both Antonio and Shylock have had business dealings in the past. Shylock claims that Antonio has spit on him, called him a dog, and insulted him for lending money for profit.
He hath disgraced me and hindered me half a million, laughed at my losses, mocked at my gains, scorned my nation, thwarted my bargains, cooled my friends, heated mine enemies—and what’s his reason?
Shylock says his famous lines about how a Jew is no different than a Christian,
I am a Jew. Hath not a Jew eyes? Hath not a Jew hands, organs, dimensions, senses, affections, passions?