By Rabbi Berach Steinfeld
The Tur in Orach Chaim, siman resh samech zayin tells us that when we daven Maariv on Shabbos we don’t finish the bracha of Hashkiveinu with the words of Shomer amo yisroel lo’ad like we do during the week because we do not need special shmira on Shabbos. The Midrash says that Shabbos does the protecting.
The Rokeach in his pirush on seder haTefillah explains that we say “haporeis sukkas shalom” not “shomer amo yisroel lo’ad” because Shabbo
Why do we need to say krias Shema al hamita with all the pesukim that serve as a shmira on Shabbos if Shabbos
We can ask another related question about shmira in regard to mezuzah. The Rema in Yoreh Deah siman resh peh heh, seif bais says that when one leaves his house during the week, he should put his hand on the mezuzah and say Hashem yishmor tzeisi etc. Does one need to do the same on Shabbos, or is it sufficient to rely on the protection of Shabbos?
The Prisha explains that there are two types of shmira needed. The first shmira is protection from enemies. The second shmira is from the mazikin. Shabbos will protect one from his enemies, but since mazikin are common on Friday night, we therefore add the pesukim in krias Shema al hamitah.
The Taz and the Prisha give a different answer. Shabbos only protects one who keeps Shabbos properly. Unfortunately, we cannot claim that we keep the Shabbos properly because we are all familiar with the Midrash that says that had Jews kept two consecutive Shabbosos properly
Based on both of these tirutzim, it would seem that when one leaves the house one should say the posuk of Hashem Yishmor. The Kitzur Hashla says that when one leaves the house on Shabbos one should not say that posuk, but rather say the posuk of Zachor es yom haShabbos lekadsho and that will serve as protection. The Elya Rabba in Siman resh samech zayin says that one should say the regular posuk.
May we all be zocheh to Shmiras Shabbos properly and we will be zocheh that the Shabbos will protect us.