Jerusalem Talmud Moed Katan 3:6

משנה: רִבִּי אֱלִיעֶזֶר אוֹמֵר מִשֶּׁחָרַב בֵּית הַמִּקְדָּשׁ עֲצֶרֶת כַּשַּׁבָּת. רַבָּן גַּמְלִיאֵל אוֹמֵר רֹאשׁ הַשָּׁנָה וְיוֹם הַכִּפּוּרִים כָּֽרְגָלִים. וַחֲכָמִים אוֹמְרִים לֹא כְדִבְרֵי זֶה וְלֹא כְדִבְרֵי זֶה אֶלָּא עֲצֶרֶת כָּֽרְגָלִים רֹאשׁ הַשָּׁנָה וְיוֹם הַכִּפּוּרִים כַּשַּׁבָּת׃ MISHNAH: Rebbi Eliezer says, since the Temple was destroyed Pentecost is like Sabbath²⁷¹When the Temple existed, the entire week starting with Pentecost was festive occasion for holiday sacrifices. Without a Temple Pentecost is just one day like the Sabbath.. Rabban Gamliel says, New Year’s Day and the Day of Atonement are like holidays²⁷²New Year’s Day is under the rules of holidays. The Day of Atonement goes by the rules of the Sabbath but in contrast to the Sabbath no infraction is a capital crime.. But the Sages are saying not like the words of either one but Pentecost is like holidays²⁷³It is a full holiday in all Pentateuchal lists of these., New Year’s Day and the Day of Atonement are like Sabbath²⁷⁴The Mishnah states that the Seven days of mourning are stopped by Pentecost and are not to be resumed after the holiday. The question now is how does this influence the count of Thirty days?.

הלכה: דְּבֵית רִבִּי יַנַּיי אָֽמְרֵי. עֲצֶרֶת עוֹלָה שִׁבְעָה כָֽרְגָלִים. בָּעוּן קוֹמֵי רִבִּי יוֹסֵה. שְׁלֹשָׁה לִפְנֵי הָעֲצֶרֶת וַעֲצֶרֶת שִׁבְעָה הֲרֶי עֲשָׂרָה. אֶלָּא שְׁלֹשָׁה לִפְנֵי עֲצֶרֶת שִׁבְעָה. וַעֲצֶרֶת שִׁבְעָה. הֲרֵי אַרְבָּעָה עָשָׂר. אָמַר רִבִּי יוֹסֵי בֵּירִבִּי. וְכֵינִי. יוֹם אֶחָד לִפְנֵי עֲצֶרֶת מוֹנֶה חֲמִשָּׁה. לְאַחַר הָעֲצֶרֶת שְׁנַיִם מוֹנֶה אַרְבָּעָה. שְׁלֹשָׁה בָֽטְלוּ מִמֶּנּוּ גְּזֵירוֹת שִׁבְעָה. HALAKHAH: They said in the House of Rebbi Yannai: Pentecost is counted as seven like holidays.They asked before Rebbi Yose: Three preceding Pentecost, and Pentecost seven, is that ten? Or three preceding Pentecost are seven, and Pentecost seven, they are fourteen²⁷⁴The Mishnah states that the Seven days of mourning are stopped by Pentecost and are not to be resumed after the holiday. The question now is how does this influence the count of Thirty days?? Rebbi Yose the important one said, one day preceding Pentecost is counted five, two days after Pentecost are counted as four. Three, the decree of Seven is cancelled²⁷⁵Since Mishnah 5 states that the holiday is not counted for the Thirty, neither is Pentecost. All its influence is to stop the count of Seven. Babli 24b..

תַּנֵּי. אֵין מַרְאִין פָּנִים לֹא בֵרֹאשׁ הַשָּׁנָה וְלֹא בְיוֹם הַכִּיפּוּרִים. אָמַר רִבִּי שְׁמוּאֵל בַּר רַב יִצְחָק. יוֹם הַכִּיפּוּרִים שֶׁחָל לִהְיוֹת בַּשַּׁבָּת מַרְאִין בּוֹ פָנִים. כְּהָדָא רִבִּי חִזְקִיָּה הֲוָה לֵיהּ עוֹבְדָא. סְלָקוּן רַבָּנִן לְגַבֵּיהּ מַרְאִין פָּנִים מֵיחֲמֶיָא לֵיהּ אַפִּין בְּצוֹמָא רַבָּא. אֲמַר לוֹן. כְּלוּם אָֽמְרוּ אֵין מַרְאִין פָּנִים לֹא בֵרֹאשׁ הַשָּׁנָה וְלֹא בְיוֹם הַכִּיפּוּרִים לֹא מִפְּנֵי הַתְּפִילָּה. שַׁנְייָא הִיא יוֹם הַכִּיפּוּרִים שֶׁחָל לִהְיוֹת בַּשַּׁבָּת. שַׁנְייָא הִיא יוֹם הַכִּיפּוּרִים שֶׁחָל לִהְיוֹת בַּחוֹל. It was stated: One makes no consolation visits on New Year’s Day and the Day of Atonement. Rebbi Samuel bar Rav Isaac said, one makes consolation visits on the Day of Atonement which falls on a Sabbath. As the following: Something happened to Rebbi Ḥizqiah. The rabbis came to pay him a consolation visit on the Day of Atonement. He said to them, did they not say that one makes no consolation visits on New Year’s Day and the Day of Atonement? Not because of prayer? There is a difference, concerning the Day of Atonement which falls on a Sabbath; there is a difference, concerning the Day of Atonement which falls on a weekday.