Tom Palmer is very fond of this quotation from Voltaire on the connections among commerce, toleration, and the erosion of prejudice:
Go into the Exchange in London, that place more venerable than many a court, and you will see representatives of all the nations assembled there for the profit of mankind. There the Jew, the Mahometan, and the Christian deal with one another as if they were of the same religion, and reserve the name of infidel for those who go bankrupt. There the Presbyterian trusts the Anabaptist, and the Church of England man accepts the promise of the Quaker. On leaving these peaceable and free assemblies, some go to the synagogue, others in search of a drink; this man is on the way to be baptized in a great tub in the name of the Father, by the Son, to the Holy Ghost...
You can find it in Tom's essay "Globalization and Culture," which is included in Realizing Freedom: Libertarian Theory, History, and Practice.
I found a very similar thought in a Wall Street Journal review of the book Ghetto at the Center of the World by Gordon Mathews. The book focuses on "the most notorious flophouse in Asia," which accommodates people from all over the world, but especially from Africa and South Asia and especially merchants who trade cheap Chinese-made goods to buyers from other countries. The review notes:
Interpersonal relations at the building, the author says, might not be reliably friendly, but "they are generally peaceful." He adds: "As a Pakistani said to me vis-à-vis Indians, 'I do not like them; they are not my friends. But I am here to make money, as they are here to make money. We cannot afford to fight.' "
Voltaire and Mathews, like many other observers, have noticed that people trying to make money don't generally get too upset about other people's race or religion. This is part of the "doux commerce" or "sweet commerce" thesis that goes back to the Middle Ages. Albert O. Hirschman wrote about it in 1982, and much of Deirdre McCloskey's current work explores the idea of "doux commerce" and bourgeois virtues.