In Lev 23:24 the text says
Speak to the children of Israel saying, In the seventh month on the first of the month there shall be for you a Sabbath, a memorial (זכרון) of trumpet sound, a holy gathering.
The day itself is called יום תרועה in Num 29:1
Now in the seventh month, on the first day of the month, you shall also have a holy convocation; you shall do no laborious work. It will be to you a day for blowing trumpets (יום תרועה).
What is meant by זכרון in Lev 23:24? The word itself is formed on the verb זכר , “to remember,” and is usually translated a “memorial,” a “remembrance,” or a “reminder.” Thus, Yom Teruah is a day on which the shofar is to be blown, and the purpose of blowing the shofar is to evoke a reminder. But of what does it remind, and who is to be reminded?
But of what does it remind, and who is to be reminded? Some of the Sages taught that the sounding of the shofar on Yom Teruah was a reminder of the kingdom of God, based on the fact that the shofar was sounded at the time of a king’s coronation (1Ki 1:39, cf. Sipra Emor; b.Rosh HaShanah 16a). Extending this idea, others taught that on Rosh HaShanah, the fate of the world was decided (m.Rosh- HaShanah 1:2), and that the sound of the shofar was to call the people to a somber reckoning of themselves in light of the enactment of God’s judgment as the ruling King. But Yom Teruah is not a dour day. In Neh 8, we read that it was the first day of the seventh month when Ezra the scribe read the Torah to the people. As it was translated for the people, they began to weep and they bowed themselves to the ground in worship of the Almighty. Then we hear Nehemiah’s exhortation to the returned exiles (vv. 9– 12):
Then Nehemiah, who was the governor, and Ezra the priest and scribe, and the Levites who taught the people said to all the people, “This day is holy to the LORD your God; do not mourn or weep.” For all the people were weeping when they heard the words of the Torah. Then he said to them, “Go, eat of the fat, drink of the sweet, and send portions to him who has nothing prepared; for this day is holy to our Lord. Do not be grieved, for the joy of the LORD is your strength.” So the Levites calmed all the people, saying, “Be still, for the day is holy; do not be grieved.” All the people went away to eat, to drink, to send portions and to celebrate a great festival, because they understood the words which had been made known to them.
Thus, the idea that Yom Teruah is a day of judgment, and that the sounding of the shofar is a reminder to Israel of this fact, does not fit with the words of Nehemiah.
In the Midrash on Lev, R. Josiah gives another explanation (based upon Ps 89:16):
R. Josiah said: It is written, ‘Happy is the people that know the sound of teruah’(Ps 89:16). But do not the nations of the world know how to sound the teruah? What a host of horns they have! What a host of bucinae (horns) they have! What a host of trumpets they have! Yet you say, ‘Happy is the people that know the sound of teruah!’ It can only mean that they know to win over their Creator with the teruah. (Mid. Rab. Lev 29.4)
In this way, the Sages taught that the sounding of the shofar was to be an instrument of prayer, one that cries out to God as a remembrance of Israel’s needs. Some have explained this to have particular connection to the time in the year that Yom Teruah occurs, that is, in the seventh month which ends the agricultural season. As such, having gathered in the final harvests of produce, Israel is to recognize that the coming agricultural year depends upon God sending rain. Thus, some teach that the call of the shofar is to remind God of Israel’s need for rain in the coming agricultural season (so Milgrom, Leviticus, in the Anchor Bible, p. 2018).
But I would suggest something different. It is granted that the Torah speaks of things that are a “memorial to God” such as the rainbow (Gen 9:16) and the Sabbath (Ex 31:17), which function to “remind” Him of His covenant promises. However, it seems to me that Ps 89:16 is better understood to mean that Israel is blessed when she knows what the sound of the shofar means, what its significance is, not (as R. Josiah teaches) as a means of reminding God by an act of prayer. Rather, the blowing of the shofar in the seventh month is to be a reminder to Israel of the counting of years, with an eye to the sh’mittah (sabbatical year) and ultimately to the Yovel or Jubilee year. Since the counting of the years was very important, not only from the standpoint of the need to comply with the laws of the sabbatical and Jubilee years, but also from a salvation-history point of view, the marking of each year was of strategic importance.
Throughout the teachings of Yeshua, the eschatological day of restoration is often in view. This may be symbolically represented as the day of harvest (as in the parable of the Sower or the Wheat and Tares, Matt 13) or the time of counting flocks, as in Matt 25:32–33,
All the nations will be gathered before Him; and He will separate them from one another, as the shepherd separates the sheep from the goats; and He will put the sheep on His right, and the goats on the left.
Indeed, all of the parables of Matthew 25 deal with the eschaton and particularly the day of judgment that comes in the last days. In the parable of the Bridesmaids, those who are wise prepare for the coming of the bridegroom but those who are foolish fail to bring sufficient oil. When the bridegroom arrives, the wise Maidens go out to meet Him with the lamps burning bright, but the foolish ones have run out of oil. While the wise Maidens accompany Him to the wedding feast, the foolish ones must go to buy more oil from the merchants, and when they finally do arrive at the wedding feast, the Groom rejects them with these words: “Truly I say to you, I do not know you.” This parallels the words of Yeshua in Matt 7:22– 23
Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ And then I will declare to them, ‘I never knew you; DEPART FROM ME, YOU WHO PRACTICE LAWLESSNESS [Ps 6:8[9]).’
He then goes on to give the parable of the wise and foolish man, and the one who builds his house upon a firm foundation, and the other who builds on the sand. Once again, the picture is preparation for the future. The wise man builds on the foundation in order to be prepared for the storm, a picture of judgment. The foolish man builds on the sand and as a result, when the storm comes (judgment day), his structure is destroyed.
The second parable of Matt 25 is that of the man who goes on a journey and entrusts his wealth to his slaves. The parable of the Talents likewise has the eschatological day of judgment in view, for the manner in which the slaves invest and increase the owner’s wealth is directly proportionate to how they fare in the judgment. Like the parable of the Sower, in which the seed yielding 30, 60, or 100 fold are all accepted as worthy, so the slave who produces five additional talents as well as the one who produces only two additional are both praised with the words “Well done, good and faithful servant. You were faithful in a few things, I will put you in charge of many things; enter into the joy of your master.” But the slave who hid the single talent and produced nothing extra is designated as “wicked” (v. 26) and is sent to the “outer darkness; in that place there will be weeping and gnashing of teeth” (v. 30).
It is no accident that the Apostle Paul speaks of the final coming of Messiah, His coming in the eschaton, as being announced by the sound of a trumpet:
For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Messiah will rise first. Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord. Therefore comfort one another with these words. (1Thess 4:16–17)
No one in the 1st Century Jewish community could have missed the fact that the reference to the “trumpet of God” (σάλπιγγι θεοῦ, salpingi theou) tied this event together with Yom Teruah, the day of sounding the trumpet, and particularly with Yom Kippur in connection with the Yovel (Jubilee) Year. For we note in Lev 25:8–12,
You are also to count off seven sabbaths of years for yourself, seven times seven years, so that you have the time of the seven sabbaths of years, namely, forty-nine years. You shall then sound a ram’s horn abroad on the tenth day of the seventh month; on the day of atonement you shall sound a horn all through your land. You shall thus consecrate the fiftieth year and proclaim a release through the land to all its inhabitants. It shall be a jubilee for you, and each of you shall return to his own property, and each of you shall return to his family. You shall have the fiftieth year as a jubilee; you shall not sow, nor reap its aftergrowth, nor gather in from its untrimmed vines. For it is a jubilee; it shall be holy to you. You shall eat its crops out of the field.
Thus, the celebration of Yom Teruah, and the solemn observance of Yom Kippur both have the eschaton and particularly the day of judgment in view. The sounding of the Shofar on Yom Teruah is to be a zikaron in the sense of proclaiming the year as it figures into the calculation of the shemittah cycle and ultimately in the calculation of the Yovel. Each Yom Teruah the people of Israel were to have this in mind: the Yovel is coming. Moreover, since the Yovel is officially announced by the blowing of the shofar, the sounding of the shofar at each Yom Teruah as well as (traditionally) at the conclusion of Yom Kippur was to remind the people that they should be preparing for the Yovel. In the sequence of the Festivals, the blowing of the shofar on Yom Kippur was the “last trumpet,” for the Torah does not mention the blowing of the shofar in connection with Sukkot.
Once again, this must surely be what Paul has in mind in 1Cor 15:50–58:
Now I say this, brethren, that flesh and blood cannot inherit the kingdom of God; nor does the perishable inherit the imperishable. Behold, I tell you a mystery; we will not all sleep, but we will all be changed, in a moment, in the twinkling of an eye, at the last trumpet; for the trumpet will sound, and the dead will be raised imperishable, and we will be changed. For this perishable must put on the imperishable, and this mortal must put on immortality. But when this perishable will have put on the imperishable, and this mortal will have put on immortality, then will come about the saying that is written, “DEATH IS SWALLOWED UP in victory. “O DEATH, WHERE IS YOUR VICTORY? O DEATH, WHERE IS YOUR STING?” The sting of death is sin, and the power of sin is the law; but thanks be to God, who gives us the victory through our Lord Messiah Yeshua. Therefore, my beloved brethren, be steadfast, immovable, always abounding in the work of the Lord, knowing that your toil is not in vain in the Lord.
This does not necessarily mean that the return of our Messiah in the eschaton will coincide with Yom Teruah or Yom Kippur, for the connection is not so much in alerting us to the day of His return but to the manner of it. Or to say it another way: our celebration of Yom Teruah and our observance of Yom Kippur is not so much marking the time of Yeshua’s return but as a reminder of what will be the consequences or effect of His return. The sounding of the Shofar is to remind us that we must be preparing for His return because when He does come, the day of judgment has arrived. We are therefore encouraged and reminded to be always preparing for His coming by sanctifying ourselves to Him through obedience of life and duties. The Shofar blasts tell us to be ready to receive the Groom and to enter into His dwelling with Him, which is the emphasis of Sukkot.