כל מלאכה לא תעשו חוקת עולם לדורותיכם… (אמור כג:לא)

There is another day that work is prohibited, namely Yom Kippur, which is holier than Shabbos, and we are commanded to fast.  However, the words “חוקת עולם לדורותיכם” are not mentioned.  Says the Meshech Chochma that this is so because, at one point in the history of Am Yisroel, they did not fast on Yom Kippur.  This occurred by Shlomo Hamelech – King Solomon, when he dedicated the first Beis HaMikdash, and the celebrations overlapped with Yom Kippur.