Responsa for Shabbat 138:9
מתקיף לה רב נחמן בר יצחק אדרבה איפכא מסתברא ושמרו בני ישראל את השבת שמירה אחת לכל שבת ושבת ואת שבתותי תשמורו שמירה אחת לשבתות הרבה:
except on that day. And on that day he is to die? — He prepared double his requirements on the previous day. But perhaps the previous day was the Sabbath? But every day he does sufficient for his requirements, and even on that day. Then wherein may that day be recognized? By kiddush and habdalah.<span class="x" onmousemove="('comment',' Kiddush =sanctification; habdalah=distinction. The former is a prayer recited at the beginning of the Sabbath; the latter is recited at the end thereof, and thanks God for making a distinction between the sanctity of the Sabbath and the secular nature of the other days of the week. ');"><sup>15</sup></span> Raba said: If he recognizes the relationship to the day of his departure,<span class="x" onmousemove="('comment',' On the day that he discovers that he has forgotten when it is the Sabbath, he nevertheless remembers how many days it is since he set out. The passage may also possibly be translated: if he recognizes a part, viz., the day on which he set out. ');"><sup>16</sup></span>
Maharach Or Zarua Responsa
R. Hayyim Eliezer recalls that one time, the winterhouse was once heated by a Gentile on the Sabbath, and his father refused to eat therein. R. Samuel of Falaise in the name of R. Yom Tov permitted one to dwell in a winterhouse that was warmed by a Gentile on the Sabbath. In our city, most of the people rely upon this decision and dwell in winterhouses that are warmed by Gentiles on the Sabbath.