Chagigah 17

גמ׳ א"ר אלעזר א"ר אושעיא מניין לעצרת שיש לה תשלומין כל שבעה שנאמר (דברים טז, טז) בחג המצות ובחג השבועות ובחג הסוכות מקיש חג השבועות לחג המצות מה חג המצות יש לה תשלומין כל שבעה אף חג השבועות יש לה תשלומין כל שבעה ואימא מקיש לחג הסוכות מה חג הסוכות יש לה תשלומין כל שמונה אף חג השבועות יש לה תשלומין כל שמונה שמיני רגל בפני עצמו הוא

Chagigah 17a:5-6

GEMARA: Rabbi Elazar said that Rabbi Oshaya said: From where is it derived that the Shavuot offerings can be redressed, i.e., that the obligatory Festival offerings can be sacrificed all seven days following the Festival? As it is stated: “Three times a year all your males shall appear…on the festival of Passover, and on the festival of Shavuot, and on the festival of Sukkot” (Deuteronomy 16:16). The verse compares the festival of Shavuot to the festival of Passover by analogy: Just as one can redress the failure to bring the offering on the festival of Passover on all seven days of the Festival, so too, on the festival of Shavuot, one can redress the failure to bring the offering for all seven, i.e., Shavuot and the six days following it. The Gemara raises a difficulty: But perhaps you should say instead that the verse compares Shavuot to the festival of Sukkot by analogy: Just as the Festival day of Sukkot can be redressed for all eight days, as the Eighth Day of Assembly is part of the Festival, so too can the festival of Shavuot be redressed for all eight days. The Gemara answers: The Eighth Day of Assembly is an independent pilgrimage Festival and is not considered part of Sukkot.

רש"י על חגיגה י״ז א:ה׳:א׳

גמ' מה חג המצות יש לה תשלומין כל שבעה - כדרבינן קראי בפ"ק (דף ט.) (בחג) הסוכות וה"ה לחג המצות שהרי אף הוא שבעת ימים:

Rashi on Chagigah 17a:5:1

Gemara- Just like Pesach has tashlumin for all 7 days- as we learned in the first chapter- we know it from Succos and it is also true for Pesach for it is also seven days.

חגיגה ט׳ א:י׳-י״א

ותנא מייתי לה מהכא דתניא (ויקרא כג, מא) וחגותם אותו חג לה' שבעת ימים יכול יהא חוגג והולך כל שבעה ת"ל אותו אותו אתה חוגג ואי אתה חוגג כל שבעה אם כן למה נאמר שבעה לתשלומין ומנין שאם לא חג יו"ט הראשון של חג שחוגג והולך את כל הרגל ויום טוב האחרון ת"ל (ויקרא כג, מא) בחדש השביעי תחגו אותו אי בחדש השביעי יכול יהא חוגג והולך החדש כולו ת"ל אותו אותו אתה חוגג ואי אתה חוגג חוצה לו

Chagigah 9a:10-11

The Gemara comments: And a tanna cites proof from here, as it is taught in a baraita with regard to a verse that deals with the festival of Sukkot: “And you shall keep it a feast to the Lord seven days” (Leviticus 23:41). One might have thought that one may continue to celebrate by bringing the Festival peace-offering all seven days of the Festival. Therefore, the verse states: “It,” which teaches: It, i.e., the first day of the Festival, you shall celebrate with these offerings, and you may not celebrate all seven days. If so, why is “seven” stated? For redress, i.e., if one failed to bring an offering on the first day he may do so all seven days. And from where is it derived that if one did not celebrate by bringing the Festival peace-offering on the first day of the festival of Sukkot that he may continue to celebrate throughout the pilgrimage Festival and even on the last festival day of Sukkot, which is the Eighth Day of Assembly? The verse states: “You shall keep it in the seventh month” (Leviticus 23:41), which indicates that one may bring the Festival offerings even after the seven days of the Festival. If the verse said only: “In the seventh month,” one might have thought that one may continue to celebrate by bringing the offering at any time during the rest of the entire month. Therefore, the verse states: “It,” indicating that you celebrate it, i.e., any of the Festival days, and you may not celebrate outside of these days.

משנה תורה, הלכות שביתת יום טוב ז׳:א׳

(א) חֻלוֹ שֶׁל מוֹעֵד אַף עַל פִּי שֶׁלֹּא נֶאֱמַר בּוֹ (ויקרא כג כד) (ויקרא כג לט) "שַׁבָּתוֹן" הוֹאִיל וְנִקְרָא (ויקרא כג ז) "מִקְרָא קֹדֶשׁ" וַהֲרֵי הוּא זְמַן חֲגִיגָה בַּמִּקְדָּשׁ אָסוּר בַּעֲשִׂיַּת מְלָאכָה כְּדֵי שֶׁלֹּא יִהְיֶה כִּשְׁאָר יְמֵי הַחל שֶׁאֵין בָּהֶן קְדֻשָּׁה כְּלָל. וְהָעוֹשֶׂה בּוֹ מְלָאכָה הָאֲסוּרָה מַכִּין אוֹתוֹ מַכַּת מַרְדּוּת מִפְּנֵי שֶׁאִסּוּרוֹ מִדִּבְרֵי סוֹפְרִים. וְלֹא כָּל מְלֶאכֶת עֲבוֹדָה אֲסוּרָה בּוֹ כְּיוֹם טוֹב שֶׁסּוֹף הָעִנְיָן בַּדְּבָרִים שֶׁנֶּאֶסְרוּ בּוֹ כְּדֵי שֶׁלֹּא יִהְיֶה כְּיוֹם חֹל לְכָל דָּבָר. לְפִיכָךְ יֵשׁ מְלָאכוֹת אֲסוּרוֹת בּוֹ וְיֵשׁ מְלָאכוֹת מֻתָּרוֹת בּוֹ:

Mishneh Torah, Rest on a Holiday 7:1

(1) Although the Torah does not attach complete rest to the intermediate days of Pesaḥ and Sukkoth, it refers to them as sacred assembly, and the pilgrim-offering was presented in the Temple on those days; hence, work is forbidden on Hol ha-Mo'ed, so that it may not be regarded as ordinary weekdays that are devoid of all sanctity. If anyone performs prohibited work on Hol ha-Mo'ed, he is punished for disobeying a rabbinic enactment. However, not every type of work is prohibited on Hol ha-Mo'ed as on a holyday, for the things that are prohibited on Hol ha-Mo'ed are essentially designed to show that it is not like a weekday in every respect. Therefore, some kinds of work are forbidden on Hol ha-Mo'ed, while others are permitted.

מועד קטן י״ט א:ז׳-ח׳

מפני שאמרו שבת עולה ואינה מפסקת רגלים מפסיקין ואינן עולין ר' אליעזר אומר משחרב בית המקדש עצרת כשבת

Moed Katan 19a:7-8

This is because the Sages said a principle with regard to this issue: Shabbat counts as one of the days of mourning, although one may not mourn on it and it does not interrupt the mourning period, which continues after Shabbat. The pilgrimage Festivals, on the other hand, interrupt the mourning period, so that if one began mourning before such a Festival, then the mourning period is canceled by the Festival. They do not, however, count. If one did not begin mourning before the Festival, or if his relative died during the Festival, then he is required to complete his mourning period afterward, as the days of the Festival do not count toward the requisite days of mourning. Rabbi Eliezer says: From the time that the Temple was destroyed, Shavuot is like Shabbat, because nowadays the days following Shavuot are not treated like Festival days. When the Temple stood, many of the Festival’s offerings that could not be sacrificed on Shavuot itself would be sacrificed during the six days following the Festival. Nowadays, however, when offerings are no longer sacrificed, Shavuot lasts for only one day in Eretz Yisrael, and therefore it is treated like Shabbat with regard to mourning: It counts as one of the days of mourning, but does not interrupt the period of mourning.