Q. Can a Gentile who accepted the seven mitzvot and accepted becoming a Ger Toshav keep Shabbat?
A. Ger Toshav is the term used to designate the legal status of a Gentile living in the Land of Israel who doesn’t want to convert to Judaism but agrees to observe the Seven Noahide Mitzvos. Any Gentile who accepts the seven commandments and is careful to observe them is of the “pious of the nations of the world” and will have a portion in the World to Come.
Rashi, (Yevamos 48b) maintains that a resident alien or Ger Toshav is obliged to observe Shabbat. Tosafos (ibid. Zeh Ger) questions Rashi but maintains that asking a Ger Toshav to do work on Shabbos for the benefit of a Jew is a Biblical violation.
Ohr Sameach (H. Issurei Biah 14: 7) maintains that the obligation of a Ger Toshav to observe the Seven Mitzvos, differs from the rest of Bnai Noach and is similar to the keeping of them by the Jewish Nation. Ohel Mordechai quotes the Ponovicher Rov adding that since for Bnai Yisroel the desecration of Shabbos is tantamount to serving Avoda Zarah (Chulin 5a), so it is for a Ger Toshav, and therefore he has to observe Shabbos.
Mishna Berura (304: 1) rules that a Ger Toshav does not have to keep Shabbos.
There is a disagreement as to what constitutes and creates a Ger Toshav. Ritva (Makos 9a) maintains that he must accept the Seven Noahide laws before a rabbinical court of three. Rabbenu Nissim, (Avodah Zarah 67b), declares that the status of an unimmersed convert is inferior to that of a Ger Toshav because the former’s acceptance of the “yoke of the commandments” is intended to be binding only upon subsequent immersion.
Rambam (H. Avoda Zarah 10: 4) rules that he is given the right to abode in the land only after his acceptance of the Seven Mitzvos in front of a rabbinical court.
Horav Shlomo Miller’s Shlit’a opinion is that the accepted view is that the Ger Toshav must accept the Seven Noahide laws before a rabbinical court of three in order to keep Shabbos. However, the Rov maintains that this type of acceptance does not apply in our days.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a