Parshat Yitro brings us to Mount Sinai and the pinnacle of the journey through the wilderness with Moshe and Bnei Yisrael receiving the Torah and the Ten commandments. The fourth comandment to keep Shabbat, begins with the word “zachor” remember the shabbat but in the repeat in Parshat Va’etchanan it begins with “shamor” keep shabbat. The Talmud in Shavuot tells us “remember and keep were spoken as one word” as we sing on Friday night in Lecha Dodi (zachor veshamor bedibur echad) which presents us with a message that these are the two inseparable elements of Shabbat. R B H Epstein explains that keeping Shabbat in terms of what you are allowed and not allowed to do is not enough, we must add to it a special level of joy for ourselves and our families, as we do, by wearing our best clothes, eating fine food and more.
However there are more differences in the first and second text. Hashem gives the reason for keeping Shabbat the first time as Hashem rested on the seventh day after six days of creation but in the repeat we are told that we should remember that we were slaves in Egypt. The Kli Yakar explains that, as we know, Hashem offered the Torah to other nations but they were not interested and for that reason the first text is more universal whereas the second text is specifically for the Jewish nation. In fact it is true that the whole world recognizes the need for a rest day and most civilizations have taken on the concept of a seven day week. I remember asking about in Japan and apparently the ancient civilization had a different week structure but they as most other civilizations have adopted the seven day week.
The Lecha Dodi composed by R Shlomo Alkabetz in the 16th century is a wonderful prayer which you will find sung wherever you may pray in the world and has some fascinating mystical messages. Read the second verse carefully this Friday night, it closes “the final result is what was in mind from the first thought.” Now if you look at how Shabbat is presented in the fourth commandment it says “keep the Shabbat day six days you shall work” and not the way you might expect, work for six days and then keep Shabbat. Hashem created the world with Shabbat in mind, that special day that we all look forward to each week. It is not just a rest from creation but in a sense a creation on its own and so we are commanded “shamor” keep it special.
Keeping Shabbat while travelling can be a challenge, especially when you stay in a hotel with electronic keys. Recently there have been halachic reponsa on the topic and well respected authority, R Nachum Rabinowitz has ruled that as there is no closing of a circuit and modern electronic devices work differently and so one may use the keys, there are of course other halachic authorities who disagree. Now everyone should decide for themselves but here is a summary in English http://frydman.co.il/hd1.pdf