Charles Ellicott Commentary Deuteronomy 23:19-20

"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 goest in to possess it." — Deuteronomy 23:19-20 (ASV)

Usury: See Exodus 22:25; Leviticus 25:35–36. Some recent writers on this law have thought that it forbids the putting out of money to interest. But it is noticeable that in both the previous passages referred to (in Exodus and Leviticus) the loan is supposed to be made to a “poor man” in “real distress.” Usury in such cases means oppression; and so it is proved to be by the examples given in Nehemiah 5:2-5; Nehemiah 5:10–12. The connection between this exaction and modern investments is not obvious, except in a very few cases. The Mosaic law against usury does not belong to commerce with other nations; it is part of the poor law of the land of Israel.