Commentary for Deuteronomy 28:48

מרב כל, ועבדת את אויביך בחוסר כל, “You will serve your enemies...deprived of everything.” This is another example of how G’d makes the punishment fit the crime (Sanhedrin 90). Seeing that the people did not serve the Lord when they had “plenty of everything,” they would wind up serving their enemies when being “devoid of all.” We read in Chagigah 9 that the words of Isaiah 48,10: “I have refined you, but not as silver, I test you in the furnace of poverty,” mean that G’d reviewed all the various positive attributes He could treat the Israelites with and found that only the attribute of poverty would be appropriate. The scholar Shmuel commented on this statement that this is the meaning of the popular saying: “poverty is as appropriate for the Jewish people as a red harness for a white horse.”