English: The commandment of Shabbos was given to Israel at Marah, as it is written concerning it “as Hashem your God commanded you,” and Rav Yehudah said in the name of Rav: “as He commanded you” — at Marah.
On the daf / in context: Parallel to the kibbud-av derasha; the second set of the Dibros refers back to the earlier command given at Marah.
Type of Learning
Diyuk of “ka’asher tzivcha” as pointing back to the command given at Marah.
What Is Learned
Shabbos was already obligatory from Marah; the Dibros restate a prior commandment.