"... This apparent redundancy is found in two forms: Shabbat Shabbaton, as here and in Exodus 31:15, or Shabbaton Shabbat, as in Exodus 16:23. The precise meaning of this phrase is obscure. It could mean a double rest for the body and mind or the most significant day of rest, even more important than the weekly Sabbath (Ibn Ezra). Both interpretations are difficult. In regard to the first, why is only Yom Kippur a double rest? Doesn’t one obtain a double rest on the weekly Sabbath? In respect to the second, is it true that the Bible considers Yom Kippur more significant than the weekly Sabbath? A third and fourth interpretation are also possible: it means nothing more than “this is a rest day upon which one should rest” or “the requirement to rest on the Day of Atonement and the Sabbath are more rigorous than other festivals when cooking is allowed under certain circumstances ..."