Talmud Bavli, Shabbat – Eating before Shabbat
Shabbat 23b:3
The Gemara discusses the practice of not eating a large meal on Erev Shabbat from the ninth hour (mincha gedolah) onwards, so as to eat the Shabbat meal with appetite — an indirect but essential source for understanding when eating is restricted before Shabbat Kiddush.
אָמַר רָבָא: פְּשִׁיטָא לִי, נֵר בֵּיתוֹ וְנֵר חֲנוּכָּה — נֵר בֵּיתוֹ עָדִיף, מִשּׁוּם שְׁלוֹם בֵּיתוֹ. נֵר בֵּיתוֹ וְקִידּוּשׁ הַיּוֹם — נֵר בֵּיתוֹ עָדִיף, מִשּׁוּם שְׁלוֹם בֵּיתוֹ. בָּעֵי רָבָא: נֵר חֲנוּכָּה וְקִידּוּשׁ הַיּוֹם מַהוּ? קִידּוּשׁ הַיּוֹם עֲדִיף — דִּתְדִיר, אוֹ דִילְמָא נֵר חֲנוּכָּה עֲדִיף — מִשּׁוּם פַּרְסוֹמֵי נִיסָּא? בָּתַר דְּבַעְיַהּ, הֲדַר פַּשְׁטַהּ: נֵר חֲנוּכָּה עֲדִיף, מִשּׁוּם פַּרְסוֹמֵי נִיסָּא.
Rava said: It is obvious to me that there is a fixed list of priorities. When a person is poor and must choose between purchasing oil to light a Shabbat lamp for his home or purchasing oil to light a Hanukkah lamp, the Shabbat lamp for his home takes precedence. That is due to peace in his home; without the light of that lamp, his family would be sitting and eating their meal in the dark. Similarly, if there is a conflict between acquiring oil to light a lamp for his home and wine for the sanctification [kiddush] of Shabbat day, the lamp for his home takes precedence due to peace in his home. However, Rava raised a dilemma: When the conflict is between oil for a Hanukkah lamp or wine for kiddush of Shabbat day, what is the ruling in that case? Does kiddush of Shabbat day take priority because it is frequent, i.e., it is performed every week, and there is a principle: When there is a conflict between a frequent practice and an infrequent practice, the frequent practice takes precedence? Or, perhaps the Hanukkah lamp takes precedence due to publicity of the miracle? After he raised the dilemma, he then resolved it on his own and he ruled that, in that case, the Hanukkah lamp takes precedence due to publicity of the miracle.