Rosh Hashanah appears in the Torah twice:

Vayikra 23:24- “On the seventh month, on the first of the month, you shall observe a day of rest, a zichron teru’a [‘a remembrance of sounding the shofar’], a sacred occasion”

Bamidbar 29:1 – “you shall observe a day of teru’a [sounding the shofar].”

If we want to understand the Biblical significance of this day, we have but one source to consult – the section in the Torah dealing with the chatzotzrot (trumpets) blown by the kohanim in the Beit Hamikdash. For our purposes here, the final two pesukim of that section are of particular importance: “When you go out to war in your land against the enemy that threatens you, you shall sound the trumpets, and you will be remembered before Hashem your God and be saved from your enemies. And on your days of joy, festivals and new months, you shall sound the trumpets with your ola offerings and with you shelamim offerings; they shall serve as a remembrance for you before Hashem your God; I am Hashem your God” (Bamidbar 10:9-10). In these pesukim, too, the terms “remembrance” and “sounding” appear in conjunction with one another. Wherein lies the connection between these two concepts?

First, let us note that the act of sounding a horn is not unique specifically to Rosh Hashanah. The chatzotzrot were sounded every month, on Rosh Chodesh. In Biblical times, Rosh Chodesh was a far more festive occasion than during our time, and sounding the trumpets on Rosh Chodesh is described as a “statute for Israel, a standard law for the God of Yaakov” (Tehillim 81:5). What, then, is the meaning of the “remembrance” on Rosh Chodesh? How should we understand the concept of “remembrance” on “days of joy and festivals”?

It stands to reason that “remembering” in this context refers to more than just the opposite of forgetting; it means paying special attention. After Am Yisrael’s period of bitter bondage in Egypt, the time for their redemption arrived: “God remembered His covenant… and God understood” (Shemot 2:24-5). From that moment, Benei Yisrael stood under the Almighty’s special protection and providence. On each holiday and festival, the Torah guarantees us of Hashem’s special providence: “And on your days of joy…you shall sound the trumpets… they shall serve as a remembrance for you before Hashem your God.” Sounding the trumpets is part of the celebration, part of the reality of Hashem’s unique providence over Am Yisrael. This applies each and every Rosh Chodesh. What, then, is special about Rosh Hashanah, to which the Torah refers as “Yom Teru’a” – the day of sounding the shofar?

It would seem that the uniqueness of the day stems from the uniqueness of this month. In the Torah we find two systems of festivals: the three regalim (pilgrimage festivals), and the festivals of the seventh month (Tishrei). The seventh month possesses a unique dimension of kedusha, just like the seventh day (Shabbat) and the seventh year (shemita). As the Midrash (Midrash Tehillim, 9:11) comments, “All the sevenths are beloved.” This month contains Yom Kippur, the day on which Hashem atones for Benei Yisrael’s sins, as well as Sukkot, the significance of which extends beyond its being one of the three regalim. Hashem’s providence over Am Yisrael is particularly evident during this month. Therefore, the Rosh Chodesh of this month, too, is exceptional in this regard, and is designated as a “zichron teru’a” – an expression that reflects the entire essence of the day. Naturally, then, the joy on this day must be compounded. This is indeed the implication of the narrative in Sefer Nechemya (chapter 8), which tells of this day, which was celebrated after the public reading of the Sefer Torah: “Nechemya said… Go ahead and eat delicacies, drink sweet drinks and send gifts to those who have nothing prepared, for today is sacred to our Lord. And do not be saddened, for the joy of Hashem is your source of strength… The entire nation went to eat, drink and send gifts and to observe great joy” (pesukim 9-12).