Problem: In Exodus 22:25, lending money with interest was only forbidden with the poor. But, here in Deuteronomy 23:19 it is forbidden with any other Jew. This raises two problems. First, why the change? Second, why the partiality?
Solution: First, the change from Exodus to Deuteronomy was necessary because of the change in circumstances. Perhaps it was because it became difficult, in the process of time, to determine who was to be considered poor. Hence, it was deemed necessary to extend the prohibition to all Hebrews. Otherwise, no poor person would ever have gotten a loan, since loans would only have been made to those who could pay interest on it.
Of course, usury was not forbidden with strangers (non-Jews), but only with brothers (other Jews). If this seems partial, it is only because the laws forbidding usury on the poor (or one’s brothers) were a divinely enjoined act of benevolence, not strictly a matter of business. When it comes to doing business, one is entitled to a reasonable profit on his investment. Since the risk of loss (from non-payment) must be covered, it is just to pay the investor an appropriate amount for his risk.
