The next hint is given in the biblical names for the festival, Yom Terua and Zikhron Terua, “the day of terua” and “a commemoration or remembrance of terua.” What is terua? In all other biblical contexts, it refers to a sound, usually produced by a wind instrument, though sometimes it may mean a shout or cry on the part of a crowd.

What instrument is the Torah referring to? The silver trumpets used by the Israelites in the wilderness were used to sound both a tekia and a terua, a tekia to summon the people and a terua to signal that it was time to begin a further journey (Num. 10:1–7). So the terua of Rosh HaShana might refer to a trumpet. The sages ruled out this possibility for a simple reason.

Rosh HaShana turns out not to be the only time that a terua was sounded in the seventh month. It was also sounded on the tenth of the month, Yom Kippur, in the Jubilee year, when slaves went free and ancestral land returned to its original owners. The Jubilee was the occasion of the famous words, taken directly from the biblical text, written on the Liberty Bell of America, “Proclaim liberty throughout all the land unto all the inhabitants thereof” (Lev. 25:10). The previous verse (25:9) states specifically that one should sound the terua with a shofar:

Then you shall sound the horn loud [shofar terua]; in the seventh month on the tenth day of the month, on the Day of Atonement, you shall have the horn sounded throughout the land.

Indeed the Hebrew word for Jubilee, yovel, also means a ram’s horn (Ex. 19:13). It became a simple inference to conclude that this applied to the terua of the first day of the seventh month as well.

What was special about the shofar? In several places in Tanakh it is the sound of battle (see, for example, Josh. 6; I Sam. 4; Jer. 4:19, 49:2). It could also be the sound of celebration. When King David brought the Ark into Jerusalem, he danced and the people rejoiced with “terua and the sound of the shofar” (II Sam. 6:15). But in a number of places, especially the historical books, the shofar was sounded at the coronation of a king. So we find at the proclamation of Solomon as king:

Tzaddok the priest took the horn of oil from the sacred tent and anointed Solomon. Then they sounded the shofar and all the people shouted, “Long live King Solomon!” (I Kings 1:39)

Likewise when Jehu was appointed king:

They quickly took their cloaks and spread them under him on the bare steps. Then they blew the shofar and shouted, “Jehu is king!” (II Kings 9:13)

When Absalom sought to have himself proclaimed king in the lifetime of his father, David, we read:

Then Absalom sent secret messengers throughout the tribes of Israel to say, “As soon as you hear the sound of the shofar, then say, ‘Absalom is king in Hebron!’” (II Sam. 15:10)

The book of Psalms associates the shofar not with a human king but with the declaration of God as King. A key text is Psalm 47, said in many congregations before the shofar blowing on Rosh HaShana:

God has been raised up in sound; raised, the Lord, in the voice of the shofar…. For God is King over all the earth…. (Ps. 47:6, 8)

Psalm 98 makes a clear connection between God’s kingship and His judgment:

With trumpets and the sound of the shofar, shout for joy before the Lord, the King…. For He is coming to judge the earth. He judges the world with righteousness and all nations with equity. (Ps. 98:6, 9)

We have now arrived at the second great dimension of Rosh HaShana. It is the day on which we celebrate the kingship of God. This has left its mark throughout the Rosh HaShana prayers. The key word is Melekh, “King.” The leader begins in the morning service with a dramatic rendition of HaMelekh. The third blessing of the Amida, which normally ends with the words “the holy God,” on Rosh HaShana and throughout the Ten Days of Repentance becomes “the holy King.” In particular, Musaf on Rosh HaShana begins with an entire section dedicated to malkhiyot, verses relating to divine kingship. Rosh HaShana is the day we celebrate God not just as Creator of the world, but its Ruler also.