In Parashat VaEtchanan, the Aseret HaDibrot are listed for a second time. In its description of the Mitzvah of Shabbat, the Torah offers two unique reasons for why this Mitzvah has to be kept. In Parashat Yitro, the Torah commands that Klal Yisrael should remember Maaseh Bereishit, the creation of the world, and should therefore keep Shabbat. In Parashat VaEtchanan, the Torah says that we must keep Shabbat in order to remember Yetziat Mitzrayim (Devarim 5:15). Why does the Torah offer two different reasons for this Mitzvah?
Many assorted reasons are given for this query. The Rambam in Moreh Nevuchim explains that in Yitro, the Torah is stressing the special Kedushah of Shabbat, perhaps connoting the Mitzvot Asei, positive commandments, of Shabbat. Conversely, in VaEtchanan the Torah stresses the need to rest from constructive labor on Shabbat in order to remember Yetziat Mitzrayim. The Ibn Ezra extends this latter point of the Rambam and explains that because the Torah (5:14) just forbade working non-Jewish slaves on Shabbat, the Torah elucidates that the reason for this is “Because you were slaves in Egypt.” On the other hand, the Ramban maintains that the two reasons given for Shabbat supplement each other. The Pasuk in Yitro explains that Hashem created the world and therefore Klal Yisrael must listen to Him, while in VaEtchanan the Torah proves that not only did Hashem create the world, but also that He remains involved in the world during every second of every day.
Perhaps a third explanation could be offered. There is an additional famous discrepancy between the Aseret HaDibrot listed in Parashat Yitro and those listed in VaEtchanan. In Yitro, the Pasuk states, “Zachor Et Yom HaShabbat LeKadesho,” “Remember the day of Shabbat to make it holy,” while in VaEtchanan the Pasuk states, “Shamor Et Yom HaShabbat LeKadesho,” “Guard the day of Shabbat to make it holy.” Chazal explain that the difference between ”Remember” and “Guard” is that the former refers to the Mitzvot Asei of Shabbat while the latter refers to the prohibition (Mitzvat Lo Taaseh) to engage in constructive work on Shabbat. One could suggest that the nature of the Mitzvot Asei of Shabbat is to actively mold a bond with our Creator, Hashem. Perhaps the case could be made that non-Jews also have such a requirement to feel a connection to Hashem paralleling their Mitzvah of believing in Hashem (and not worshipping idols). Therefore, the Torah in Yitro presents the universal reason why one must keep Shabbat (i.e. that Hashem created the world), a reason that applies to Jews and non-Jews alike. Conversely, non-Jews do not have a commandment to rest for one day out of the week and learn Torah while reflecting on the previous week. In fact, the Gemara in Masechet Shabbat states that if a non-Jew keeps Shabbat, he has violated an Aveirah with a punishment of death. Therefore, while describing the Issur Melachah of Shabbat, the Torah lists a reason for keeping Shabbat that applies to Jews alone, namely, that Hashem redeemed us from being slaves in Mitzrayim.