The discussion about the dietary laws in the Hertz Pentateuch commentary has a few interesting things about it. There is the sociological assertion that kashrut has proved historically to be “an important factor in the preservation of the Jewish race.” And not only that, but “an irreplaceable agency for maintaining Jewish identity in the present.” The for him rare use of the Yiddish word kashrus signals that he has in mind the mass of East European Jews and East European Jewish immigrants in England, where he was Chief Rabbi of the United Hebrew Congregations of the British Empire.
While “not a few of our co-religionists” were abandoning the synagogue, Hertz assumed and expressed confidence that the daily practice of the dietary rules would continue to sustain Jewish identity. As he saw it, “the great majority of Jews” of his day continued to abstain from unkosher food, “not only from personal aversion, but because ‘our Father in Heaven has decreed that we should abstain from it.'” This is an interesting statement concerning the practice of Jewish traditions back in the early 20th C. Also strange here is an also unusual reference to the Zohar, the idea being that “Whosoever eats forbidden foods becomes imbued with a spirit of impurity, and is cast out of the realm of divine Holiness.”
This is an interesting moment in the Hertz commentary. The extended discussion of Jewish folk/foodways and their power to preserve the race includes reference to the large numbers of Jews still observing kashrut in his day. Then there is the dropping of the term “kashrus” (is it Yiddish or Hebrew with Ashkenazi pronunciation?), the anxious expression of a theological confidence, and the reference to the Zohar. Are these little relics of old Ashkenazi folk religion undergirding the high English and bourgeois edifice of the Hertz Pentateuch?
You can find this in the introduction to the dietary laws in the opening comments to Leviticus chapter 11.