Positive commandment · Mitzvat Aseh #170 of 613
To hear the sound of the shofar on Rosh HaShanah
לשמוע קול שופר בראש השנה
The verse · Bamidbar 29:1
וּבַחֹדֶשׁ הַשְּׁבִיעִי בְּאֶחָד לַחֹדֶשׁ מִקְרָא־קֹדֶשׁ יִהְיֶה לָכֶם כׇּל־מְלֶאכֶת עֲבֹדָה לֹא תַעֲשׂוּ יוֹם תְּרוּעָה יִהְיֶה לָכֶם
“And in the seventh month, on the first day of the month, you shall have a holy gathering; you shall do no servile work: it is a day of blowing the horn to you.”
The Rambam’s words
To hear the sound of the shofar on Rosh HaShanah, as [Numbers 29:1] states: "It will be a day of [shofar] blasts for you."
לשמוע קול שופר בראש השנה, שנאמר: "יום תרועה, יהיה לכם" (במדבר כט,א).
Why · Sefer HaChinuch #405
Shofar (horn) on Rosh Hashanah
“It is from the roots of the commandment [that] since a person is physical, he is only aroused by something that arouses, like the way of people during wartime [to] blow and even scream in order that they should be properly aroused for war.”
Who & when
“And it is practiced in every place and at all times by males, but not by females; because it is in the category of commandments determined by time, [from which] women are exempt.”
Where in the Mishneh Torah
Hilchot Shofar, Sukkah and Lulav הלכות שופר וסוכה ולולב