According to Jewish Law and tradition, is it acceptable, discouraged or totally unacceptable for a Gentile to keep the Sabbath according to the regulations spelled out in the Torah and the Talmud and expounded upon by the Rabbis?
A non Jew is not allowed to keep Shabbos. Those that are in the process of converting make sure to do at least one thing on Shabbos that would normally not be allowed. For example they might carry something in their pocket.
The Torah says "The Children of Israel shall observe the Sabbath, to make the Sabbath an eternal covenant for their generations. Between Me and the Children of Israel it is a sign forever that in a six-day period Hashem made the heaven and the earth, and on the seventh day He rested and was refreshed." (Exodus 31:16,17 Artscroll Translation).
The Sabbath was given as a sign and covenant to Israel, a Gentile is forbidden to observe the Sabbath or to make a Sabbath of their own, a Halachah codified in the Mishneh Torah, Laws of Kings 10:9.
It is important to realize, however, that it is generally forbidden to instruct a non-Jew to perform anything on Shabbos that a Jew is prohibited to do by law (Orach Chaim 307:2).
I agree with Gershon Gold's answer.
I have had several Christian guests in our home over the years. Many of them wish to experience authentic Jewish practices, since they view Judaism as the source of their own religion.
I asked, on a practical level, if I have violated anything by allowing a non-Jew to keep shabbos in my house.
The answer I received was; the obligation to not keep shabbos is incumbent upon the Gentile. Therefore, I was not responsible in any way to encourage my Gentile guests to break shabbos while in my home.
(In every case, they all used their cell phones and / or computers at some point during shabbos, which may or may not be a d'oraisa, but certainly removes them from the category a shomer shabbos.)
The source for the Halacha is Talmud Sanhedrin 58B:
ואר"ל עובד כוכבים ששבת חייב מיתה שנא' ויום ולילה לא ישבותו ואמר מר אזהרה שלהן זו היא מיתתן אמר רבינא אפי' שני בשבת
Resh Lakish also said: A heathen who keeps a day of rest, deserves death, for it is written (Gen. VIII, 22), And a day and a night they shall not rest, and a master has said: Their prohibition is their death sentence. Rabina said: Even if he rested on a Monday.
Interestingly, the simple meaning of Bereshit 8:22 is not referring to people working, but rather that the heavenly bodies will never cease to function again (as they did in the flood).
Rashi on the Talmud says that the verse also refers to people (in addition to the heavenly bodies).
There is a Sicha (in Yiddish) (Likutei Sichot 15, pg 49) from the Lubavitcher Rebbe, which discusses the connection between the simple meaning of the verse and the prohibition of a gentile to keep Shabbat according to the Rambam.
Gerim are permitted to keep shabbes fully in terms of the Jewish way of counting days, i.e. from shkiah to shkiah, without violating the prohibition in Talmud Sanhedrin 58B. I have a ger friend who asked the Beis Din about this matter and got such an answer.
The reason given to us was that before we are fully converted, we are nevertheless halachically goyim. Goyim count days by sunrise to sunrise - like in a regular secular calendar. Therefore, for them to rest totally on any given full goy day (which is prohibited by the Talmud) is a different thing from resting on the Jewish way of counting a full day.
I know this is an old thread but hope it helps for anyone who revisits this thread.