Each Friday night when we recite the famous “Lecha Dodi” prayer we say the following words: “Shamor v’Zachor b’dibur echad, ‘safeguard’ and ‘remember’ in a single utterance…”

The song is referring to the miraculous way that the mitzvah of Shabbat, the fourth of the Ten Commandments was given to B’nai Yisrael.

In Parshat Yitro, Shmot 20:8 we find the words “Zachor et yom haShabbat l’kodsho”, “Rememder the Shabbat day to sanctify it”, while in Devarim 5:12 we find the words “Shamor et yom haShabbat l’kodsho”, “Safeguard the Shabbat to sanctify it”.

The Gemara in Masechet Shavuot 20b explains the when God gave the Ten Commandments He caused B’nai Yisrael to hear the words “Shamor” and “Zachor” at the exact same time. Shamor refers to the injunction not to desecrate Shabbat (mitzvat lo ta’aseh) while Zachor reminds us to keep Shabbat in our hearts and give verbal expression to its holiness (mitzvat aseh).

According to Rabbi Shimshon Raphael Hirsch, God combined both Zachor and Shamor at Sinai to show that they are inseparable. Shabbat is not just a day where we refrain from doing work, Shabbat is a spiritual day to sanctify and enjoy.

Zachor also reminds us that throughout the week we should be thinking of Shabbat and preparing for it. Rashi, quoting the Mechilta says that if you happen upon especially appetizing food then you should set it aside for Shabbat (this is where the custom of serving sugar cereals only on Shabbat is derived).

Sforno’s view is that throughout the week we should think about Shabbat while we are working so that we can push ourselves to accomplish what we need to before Shabbat starts. In that way, our minds will be clear and free of worries by the time that Shabbat comes along!