It is forbidden to give with an expectation of receiving more in return, that is, to charge interest anywhere and in anything! I cannot give you use of my donkey expecting for you to give me back two, as is common in business practice today. After all, in what you gave me is your gain, not mine, because you gave.
Jews were blamed for usury, but it was not actually usury, but interest on the debt. We are only now beginning to understand why a person must return a greater sum of money to the moneylender who lent it to him.
Torah, Deuteronomy 23:21: You may [however,] give interest to a gentile, but to your brother you shall not give interest, in order that the Lord, your God, shall bless you in every one of your endeavors on the land to which you are coming to possess.
“A foreigner” is the desire that is still aimed “for me.” In the process of correcting these desires you want to extract maximal profit for the quality of bestowal from them and reshape egoistic qualities to altruistic ones with as high an interest as possible.
In the Torah, when it is written that you can steal from non-Jews, rob them, etc., what is being referred to is the way we need to transform our egoism because the Torah only speaks about the inner correction of the individual.
From KabTV’s “Secrets of the Eternal Book” 10/26/16