Or HaChaim on Deuteronomy 32:5/אור החיים על דברים ל״ב:ה׳

1 שחת לו לא בניו מומם, "Its corruption caused them no longer to be His fit children due to their blemish." When they become corrupt they cause harm to themselves. They are no longer called the children of the living G'd as our sages have said in Baba Batra 10: "as long as the children of Israel follow the path of G'd they are called "children;" if they stray, they are called "slaves." Moses mentions that if Israel becomes corrupt vis-a-vis G'd they are no longer His children. He adds the word מומם, their blemish, to remind Israel that if it does become blemished the fault is not with G'd but with themselves. Moses had to add this so that one would not conclude that the blemish found in the Israelites must eventually be traced back to G'd Himself, to their origin. G'd had created man, i.e. Israel, ישר, morally upright; we know this from Isaiah 5,1 where G'd describes Himself as "having owned a vineyard on a fruitful hill. He broke the ground, cleared it of stones and planted it with choice vines, etc. etc. Instead it yielded wild grapes." In other words, the corruption, the blemish, developed out of the people not out of their association with G'd. We are told in Sotah 3 that one does not commit a sin until after one's mind has been invaded by a streak of madness. This is the mystical dimension of Deut. 15,21 מום רע, "a severe blemish." The continued presence of this blemish is attributable exclusively to the deeds of man.

2דור עקש ופתלתל, "a perverse and twisted generation." If the generation were smitten only with perversion the words of Torah might suffice to straighten out these people. Who is responsible for the people to have become so twisted? None other than their inherent tendency to be stiff-necked, not to be willing to admit they had been mistaken. It is tragic to be a witness to all kinds of heresy being rampant during these generations and whenever someone comes along and tries to straighten out the misguided thinking of these heretics they become reinforced and even more entrenched in their heresy. This leads to these people losing their homeland.