The stranger is here introduced in similar circumstances, to show the line of distinguishing grace.
Related Commentaries of Deuteronomy 23:20
Deuteronomy 23:20
20 Unto a stranger thou mayest lend upon usury; but unto thy brother thou shalt not lend upon usury: that the LORD thy God may bless thee in all that thou settest thine hand to in the land whither thou goest to possess it.