Pesachim 106a
פסחים ק״ו א — ד"ה תָּנוּ רַבָּנַן
Pesachim 106a:5
The Gemara discusses kiddush and the obligation to sanctify the day over wine, including the relationship between kiddush and the act of drinking.
תָּנוּ רַבָּנַן: ״זָכוֹר אֶת יוֹם הַשַּׁבָּת לְקַדְּשׁוֹ״ — זוֹכְרֵהוּ עַל הַיַּיִן. אֵין לִי אֶלָּא בְּיוֹם, בַּלַּיְלָה מִנַּיִן? תַּלְמוּד לוֹמַר: ״זָכוֹר אֶת יוֹם הַשַּׁבָּת לְקַדְּשׁוֹ״. הָכִי קָאָמַר: ״זָכוֹר אֶת יוֹם הַשַּׁבָּת לְקַדְּשׁוֹ״ — זוֹכְרֵהוּ עַל הַיַּיִן בִּכְנִיסָתוֹ, אֵין לִי אֶלָּא בַּלַּיְלָה, בַּיּוֹם מִנַּיִן? תַּלְמוּד לוֹמַר: ״זָכוֹר אֶת יוֹם הַשַּׁבָּת״.
The Sages taught in a baraita with regard to the verse: “Remember the day of Shabbat to sanctify it” (Exodus 20:7): Remember it over wine, through the recitation of kiddush. I have only derived that there is a mitzva to recite kiddush during the day, as the verse is referring to the day of Shabbat. From where do I derive that one must also recite kiddush at night? The verse states: “Remember the day of Shabbat to sanctify it,” which indicates that one should also remember Shabbat as soon as it is sanctified. The Gemara answers that this is what the tanna is saying: “Remember the day of Shabbat to sanctify it” is a mitzva to remember it over wine when it begins. I have only derived the obligation to recite kiddush at night; from where do I derive that one must also recite kiddush during the day? The verse states: “Remember the day of Shabbat.” The emphasis of the word day indicates that one must recite kiddush again during the day.