Deuteronomy 23:19

"Thou shalt not lend upon interest to thy brother; interest of money, interest of victuals, interest of anything that is lent upon interest. Unto a foreigner thou mayest lend upon interest; but unto thy brother thou shalt not lend upon interest, that Jehovah thy God may bless thee in all that thou puttest thy hand unto, in the land whither thou goes in to possess it."

See further comment on this under Exodus 22:25. This permission for Israel to loan money to foreigners definitely made the Jewish people the bankers of the human race. During the Middle Ages, when Jews, through prejudice, were forbidden to own land, they naturally turned to the banking industry, resulting in the buildup of great financial barons such as the Rothschilds and others.

The thinking behind this was that a Jew should aid his poor or needy brother with an interest-free loan, or by an outright gift.