I might think that if the year were lacking fourteen or fifteen days, you should add that number of days to it; it is, therefore, written "the month," and not less. ...
I might think that if it were lacking forty or fifty days, you should add that number of days to it; it is, therefore, written "the month" — not less and not more.
We are hereby apprised that Moses heard the order of the festivals on Sinai, repeated it to Israel, and repeated it again at the time of their occurrence,
(דברים טז א) שָׁמוֹר אֶת חֹדֶשׁ הָאָבִיב, שָׁמוֹר אֶת הַחֹדֶשׁ סָמוּךְ לָאָבִיב, מִפְּנֵי אָבִיב שֶׁיְּהֵא בִּזְמַנּוֹ.
(Devarim 16:1) "Observe the month of Aviv": Observe the month close to Aviv, so that aviv (the springtide) fall out in its proper time.
יָכוֹל אִם הָיְתָה שָׁנָה חֲסֵרָה אַרְבָּעָה עָשָׂר יוֹם אוֹ חֲמִשָּׁה עָשָׂר יוֹם, אַתָּה נוֹתֵן לָהּ אַרְבָּעָה עָשָׂר יוֹם אוֹ חֲמִשָּׁה עָשָׂר יוֹם? תַּלְמוּד לוֹמַר: חֹדֶשׁ – לֹא פָּחוֹת וְלֹא יָתֵר.
I might think that if the year were lacking fourteen or fifteen days, you should add that number of days to it; it is, therefore, written "the month," and not less. ...
יָכוֹל אִם הָיְתָה שָׁנָה חֲסֵרָה אַרְבָּעִים יוֹם אוֹ חֲמִשִּׁים יוֹם, אַתָּה נוֹתֵן לָהּ אַרְבָּעִים יוֹם אוֹ חֲמִשִּׁים יוֹם? תַּלְמוּד לוֹמַר: חֹדֶשׁ – לֹא פָחוֹת וְלֹא יָתֵר.
I might think that if it were lacking forty or fifty days, you should add that number of days to it; it is, therefore, written "the month" — not less and not more.
שָׁמוֹר אֶת חֹדֶשׁ הָאָבִיב, בִּשְׁלֹשָׁה מְקוֹמוֹת מַזְכִּיר פָּרָשַׁת מוֹעֲדוֹת: בְּתוֹרַת כֹּהֲנִים מִפְּנֵי סִדְרָן,
(Devarim 16:1) "Observe the month of Aviv": In three places the section of festivals is mentioned: In Vayikra, because of their order;
בְּחוּמַשׁ הַפְּקוּדִים מִפְּנֵי קָרְבָּן,
in Bamidbar, because of the (relevant) offerings;
בְּמִשְׁנֵה תוֹרָה מִפְּנֵי הָעִבּוּר.
in Devarim, for communal exhortation.
לְלַמֶּדְךָ שֶׁשָּׁמַע מֹשֶׁה פָּרָשַׁת מוֹעֲדוֹת וַאֲמָרָהּ לְיִשְׂרָאֵל, וְחָזַר וּשְׁנָאָהּ לָהֶם בִּשְׁעַת מַעֲשֶׂה.
We are hereby apprised that Moses heard the order of the festivals on Sinai, repeated it to Israel, and repeated it again at the time of their occurrence,
דָּבָר אַחֵר: אָמַר לָהֶם הִלְכוֹת הַפֶּסַח בַּפֶּסַח, הִלְכוֹת עֲצֶרֶת בַּעֲצֶרֶת, הִלְכוֹת חַג בֶּחָג. מִכָּן אָמְרוּ: מֹשֶׁה הִזְהִיר אֶת יִשְׂרָאֵל לִהְיוֹת שׁוֹנִים בָּעִנְיָן וְדוֹרְשִׁים בּוֹ.
Moses telling them: Take care to study these things and to expound them.