רבי יוסי בר' יהודה אומר (שמות לא, יג) את שבתותי תשמורו יכול לכל ת"ל אך חלק רבי יונתן בן יוסף אומר (שמות לא, יד) כי קודש היא לכם היא מסורה בידכם ולא אתם מסורים בידה
Other tanna’im debated this same issue. Rabbi Yosei, son of Rabbi Yehuda, says that it is stated: “But keep my Shabbatot” (Exodus 31:13). One might have thought that this applies to everyone in all circumstances; therefore, the verse states “but,” a term that restricts and qualifies. It implies that there are circumstances where one must keep Shabbat and circumstances where one must desecrate it, i.e., to save a life. Rabbi Yonatan ben Yosef says that it is stated: “For it is sacred to you” (Exodus 31:14). This implies that Shabbat is given into your hands, and you are not given to it to die on account of Shabbat.
ר' שמעון בן מנסיא אומר (שמות לא, טז) ושמרו בני ישראל את השבת אמרה תורה חלל עליו שבת אחת כדי שישמור שבתות הרבה א"ר יהודה אמר שמואל אי הואי התם הוה אמינא דידי עדיפא מדידהו (ויקרא יח, ה) וחי בהם ולא שימות בהם
Rabbi Shimon ben Menasya said: It is stated: “And the children of Israel shall keep Shabbat, to observe Shabbat” (Exodus 31:16).The Torah said: Desecrate one Shabbat on his behalf so he will observe many Shabbatot. Rav Yehuda said that Shmuel said: If I would have been there among those Sages who debated this question, I would have said that my proof is preferable to theirs, as it states: “You shall keep My statutes and My ordinances, which a person shall do and live by them” (Leviticus 18:5), and not that he should die by them. In all circumstances, one must take care not to die as a result of fulfilling the mitzvot.
אמר רבא לכולהו אית להו פירכא בר מדשמואל דלית ליה פירכא דר' ישמעאל דילמא כדרבא דאמר רבא מאי טעמא דמחתרת חזקה אין אדם מעמיד עצמו על ממונו והאי מידע ידע דקאי לאפיה ואמר אי קאי לאפאי קטילנא ליה והתורה אמרה בא להרגך השכם להרגו ואשכחן ודאי ספק מנלן
Rava commented on this: All of these arguments have refutations except for that of Shmuel, which has no refutation. The Gemara explains Rava’s claim: The proof brought by Rabbi Yishmael from the thief who breaks in could perhaps be refuted based on the principle of Rava, as Rava said: What is the reason for the halakha about the thief who breaks in? There is a presumption that while a person is being robbed he does not restrain himself with respect to his money. And this thief knows that the homeowner will rise to oppose him and said to himself from the start: If he rises against me, I will kill him. And the Torah states: If a person comes to kill you, rise to kill him first. We found a source for saving a life that is in certain danger, but from where do we derive that even in a case where there is uncertainty as to whether a life is in danger one may desecrate Shabbat? Consequently, Rabbi Yishmael’s argument is refuted.