Picture this scene: Millions of Jews — men and women, infants and their great-grandmothers, scholars and laypeople — assembled in Jerusalem on the Temple Mount. A hush falls over the mammoth crowd, as the royally bedecked king of Israel ascends onto a platform and reads sections of the holy Torah. The nation is inspired and invigorated. A display of unity and a statement of purpose converge to revitalize and refocus a multifarious people.

Though seemingly improbable, this scene repeated itself in ancient Jerusalem on a septennial basis. And when the Temple will soon be rebuilt, the practice will be renewed, with Mashiach himself reading from the Torah scroll.

At the end of every seven years, at an appointed time, in the Festival of Sukkot [following] the year of Shemitah, when all Israel comes to appear before the Lord, your G-d, in the place He will choose, you shall read this Torah before all Israel, in their ears. Assemble the people: the men, the women, the children....—Devarim/Deuteronomy 31:10-12

In ancient Israel, every seventh year was a Shemitah ("sabbatical") year. For an entire year, the nation's economy came to a standstill as all farmers and agrarian workers abandoned their fields and flocked en masse to the houses of study where, for a full year, they focused on their spiritual needs, rather than their physical needs.

Now, at the onset of the eighth year (the first in the new seven-year cycle), the nation is ready to head back to the fields and orchards. But first, on the second day of the holiday of Sukkot, sixteen days into the new year, all gather in the Holy Temple for a dose of inspiration. This inspiration is to tide them over for the next six years, most of whose time would be spent in business endeavors.

...In order that they hear, and in order that they learn and fear the Lord, your G-d, and they will observe all the words of this Torah.

—Ibid.

Reliving Mount Sinai

This event was known as Hakhel, "assemble!" It was the only event that required the attendance of every Jew, reminiscent of the historic moment when our nation stood at Mount Sinai, when every member of our nation was present as G-d lovingly gave us the Torah.

Converts [who don't understand the Hebrew tongue] are required to prepare themselves and apply their ears to listen with awe, reverence, and joyful trepidation, as on the day [the Torah] was given at Sinai. Even great scholars who are versed in the entire Torah are obligated to listen with great concentration....

—Maimonides, Laws of Chagigah 3:6

Once the entire nation had gathered, the king, situated on a specially constructed platform in the Temple's courtyard, was handed the Torah scroll that Moses himself had written. The king recited a blessing and then read aloud several portions from the Book of Deuteronomy, and then concluded with several more blessings.

...Every individual should see himself as if he is now being commanded, and it is from G-d's mouth that he is hearing these words. For the king is only the messenger to announce G-d's words

—Ibid.

The talk of all the nation — men, women, and children — would then be: "Why have we assembled for this large gathering?" And the answer would be: "To hear the words of the Torah—our essence, glory, and pride!" This would lead them to praise the Torah and speak of its glorious worth, and implant within their hearts a desire and motivation to study and know G-d. Thus they will merit the ultimate good, and G-d will rejoice in His creations....—Sefer haChinuch, mitzvah 612

Hakhel Today

The biblical mitzvah of Hakhel is only in effect when all the Jewish people reside in the Holy Land. Nevertheless, the Lubavitcher Rebbe repeatedly encouraged all Jews to utilize this auspicious time to assemble — men, women, and children — and encourage each other to increase in Torah observance and study, and foster an environment of fear of G-d.

The Rebbe particularly encouraged these assemblies on or around Sukkot, when the Hakhel gathering took place in the Holy Temple, but the entire year is a "Hakhel Year," and an opportune time to promote Jewish unity and gatherings.

The responsibility to arrange Hakhel gatherings lies primarily on the "kings," i.e., the leaders – rabbis and communal activists – of each community. But during this year everyone should be mindful of any opportunity that presents itself to gather together some Jews and recreate, in microcosm, the grand Hakhel event.

Courtesy of Chabad.org