Comentário sobre Deuteronômio 5:12

שמור OBSERVE [THE SABBATH DAY] — But in the former Ten Commandments (i.e. where they were first promulgated, in Exodus XX.), it states, “Remember [the Sabbath day]"! The explanation is: Both of them (זכור and שמור) were spoken in one utterance and as one word, and were heard in one hearing (i.e. were heard simultaneously) (Mekhilta d'Rabbi Yishmael 20:8:1).

לקדשו כאשר צוך, in the manner He had already issued commandments pertaining to Sabbath observance at Marah (Exodus 15,26)

שמור את יום השבת, "Observe the Sabbath day, etc." Rosh Hashanah 27 teaches that the formula שמור את יום השבת (in Exodus 20) and the formula שמור את יום השבת (here) were articulated simultaneously. According to this interpretation we can understand the words כאשר צוך in our verse as a reference to the word זכור in the first report of the Ten Commandments in the Book of Exodus. We find in the Mechilta on the parallel verse in Exodus that the word שמור was enunciated later. [The Mechilta there quotes other examples of laws which were articulated by G'd simultaneously, i.e. by His using two words to describe them, and which also had to be written separately due to our limited ability to reproduce words articulated simultaneously as such. Ed.] We must ask why the Torah did not write the words זכור and שמור sequentially in Exodus instead of waitng till here to write this word. Perhaps the Torah intentionally separated these words in order that we should not think that the latter expression refers to the time during which the זכור aspect of the Sabbath applies. We might have understood the two words to mean: "remember to observe the Sabbath (at a certain time)." By separating the apparance of these two words the Torah conveyed that it spoke about two separate commandments one of which applies at the beginning of the Sabbath, the other at its conclusion. It is even possible that G'd Himself only uttered the word זכור; however, intelligent people realised that this word implied both the meaning associated with the word זכור and the meaning associated with the word שמור.