Bava Metzia 71 - Taking Interest from Non-Jews is also Prohibited
King Solomon and his court prohibited taking interest from non-Jews, as it says in Proverbs, " One who increases his wealth by interest collects it for he who favors the poor "- and who will distribute the interest to the poor after the usurer's demise.
The reason for this prohibition is that if the financier becomes used to taking interest, he may come to take it from Jews also. Excluded are cases of small interest, "enough to live on" and Torah scholars, who knows the law and will not come to take interest from the Jews. Later on, taking interest from non-Jews became permitted, since it was not possible otherwise.