Sources in Tanakh for Rosh Hashanah 34a
(כד) דַּבֵּ֛ר אֶל־בְּנֵ֥י יִשְׂרָאֵ֖ל לֵאמֹ֑ר בַּחֹ֨דֶשׁ הַשְּׁבִיעִ֜י בְּאֶחָ֣ד לַחֹ֗דֶשׁ יִהְיֶ֤ה לָכֶם֙ שַׁבָּת֔וֹן זִכְר֥וֹן תְּרוּעָ֖ה מִקְרָא־קֹֽדֶשׁ׃
(24) Speak to the Israelite people thus: In the seventh month, on the first day of the month, you shall observe complete rest, a sacred occasion commemorated with loud blasts.

(ד) וּבַשָּׁנָ֣ה הַשְּׁבִיעִ֗ת שַׁבַּ֤ת שַׁבָּתוֹן֙ יִהְיֶ֣ה לָאָ֔רֶץ שַׁבָּ֖ת לַה' שָֽׂדְךָ֙ לֹ֣א תִזְרָ֔ע וְכַרְמְךָ֖ לֹ֥א תִזְמֹֽר: .... (ח) וְסָפַרְתָּ֣ לְךָ֗ שֶׁ֚בַע שַׁבְּתֹ֣ת שָׁנִ֔ים שֶׁ֥בַע שָׁנִ֖ים שֶׁ֣בַע פְּעָמִ֑ים וְהָי֣וּ לְךָ֗ יְמֵי֙ שֶׁ֚בַע שַׁבְּתֹ֣ת הַשָּׁנִ֔ים תֵּ֥שַׁע וְאַרְבָּעִ֖ים שָׁנָֽה׃ (ט) וְהַֽעֲבַרְתָּ֞ שׁוֹפַ֤ר תְּרוּעָה֙ בַּחֹ֣דֶשׁ הַשְּׁבִעִ֔י בֶּעָשׂ֖וֹר לַחֹ֑דֶשׁ בְּיוֹם֙ הַכִּפֻּרִ֔ים תַּעֲבִ֥ירוּ שׁוֹפָ֖ר בְּכָל־אַרְצְכֶֽם׃ (י) וְקִדַּשְׁתֶּ֗ם אֵ֣ת שְׁנַ֤ת הַחֲמִשִּׁים֙ שָׁנָ֔ה וּקְרָאתֶ֥ם דְּר֛וֹר בָּאָ֖רֶץ לְכָל־יֹשְׁבֶ֑יהָ יוֹבֵ֥ל הִוא֙ תִּהְיֶ֣ה לָכֶ֔ם וְשַׁבְתֶּ֗ם אִ֚ישׁ אֶל־אֲחֻזָּת֔וֹ וְאִ֥ישׁ אֶל־מִשְׁפַּחְתּ֖וֹ תָּשֻֽׁבוּ׃

(4) But in the seventh year the land shall have a sabbath of complete rest, a sabbath of the LORD: you shall not sow your field or prune your vineyard..... (8) You shall count off seven weeks of years—seven times seven years—so that the period of seven weeks of years gives you a total of forty-nine years. (9) Then you shall sound the horn loud; in the seventh month, on the tenth day of the month—the Day of Atonement—you shall have the horn sounded throughout your land (10) and you shall hallow the fiftieth year. You shall proclaim release throughout the land for all its inhabitants. It shall be a jubilee for you: each of you shall return to his holding and each of you shall return to his family.

(א) וּבַחֹ֨דֶשׁ הַשְּׁבִיעִ֜י בְּאֶחָ֣ד לַחֹ֗דֶשׁ מִֽקְרָא־קֹ֙דֶשׁ֙ יִהְיֶ֣ה לָכֶ֔ם כָּל־מְלֶ֥אכֶת עֲבֹדָ֖ה לֹ֣א תַעֲשׂ֑וּ י֥וֹם תְּרוּעָ֖ה יִהְיֶ֥ה לָכֶֽם׃
(1) In the seventh month, on the first day of the month, you shall observe a sacred occasion: you shall not work at your occupations. You shall observe it as a day when the horn is sounded.
(א) וַיְדַבֵּ֥ר ה' אֶל־מֹשֶׁ֥ה לֵּאמֹֽר׃ (ב) עֲשֵׂ֣ה לְךָ֗ שְׁתֵּי֙ חֲצֽוֹצְרֹ֣ת כֶּ֔סֶף מִקְשָׁ֖ה תַּעֲשֶׂ֣ה אֹתָ֑ם וְהָי֤וּ לְךָ֙ לְמִקְרָ֣א הָֽעֵדָ֔ה וּלְמַסַּ֖ע אֶת־הַֽמַּחֲנֽוֹת׃ (ג) וְתָקְע֖וּ בָּהֵ֑ן וְנֽוֹעֲד֤וּ אֵלֶ֙יךָ֙ כָּל־הָ֣עֵדָ֔ה אֶל־פֶּ֖תַח אֹ֥הֶל מוֹעֵֽד׃ (ד) וְאִם־בְּאַחַ֖ת יִתְקָ֑עוּ וְנוֹעֲד֤וּ אֵלֶ֙יךָ֙ הַנְּשִׂיאִ֔ים רָאשֵׁ֖י אַלְפֵ֥י יִשְׂרָאֵֽל׃ (ה) וּתְקַעְתֶּ֖ם תְּרוּעָ֑ה וְנָֽסְעוּ֙ הַֽמַּחֲנ֔וֹת הַחֹנִ֖ים קֵֽדְמָה׃ (ו) וּתְקַעְתֶּ֤ם תְּרוּעָה֙ שֵׁנִ֔ית וְנָֽסְעוּ֙ הַֽמַּחֲנ֔וֹת הַחֹנִ֖ים תֵּימָ֑נָה תְּרוּעָ֥ה יִתְקְע֖וּ לְמַסְעֵיהֶֽם׃ (ז) וּבְהַקְהִ֖יל אֶת־הַקָּהָ֑ל תִּתְקְע֖וּ וְלֹ֥א תָרִֽיעוּ׃
(1) The LORD spoke to Moses, saying: (2) Have two silver trumpets made; make them of hammered work. They shall serve you to summon the community and to set the divisions in motion. (3) When both are blown in long blasts, the whole community shall assemble before you at the entrance of the Tent of Meeting; (4) and if only one is blown, the chieftains, heads of Israel’s contingents, shall assemble before you. (5) But when you sound short blasts, the divisions encamped on the east shall move forward; (6) and when you sound short blasts a second time, those encamped on the south shall move forward. Thus short blasts shall be blown for setting them in motion, (7) while to convoke the congregation you shall blow long blasts, not short ones.
(ד) תִּקְע֣וּ בַחֹ֣דֶשׁ שׁוֹפָ֑ר בַּ֝כֵּ֗סֶה לְי֣וֹם חַגֵּֽנוּ׃
(4) Blow the horn on the new moon, on the full moon for our feast day.