The 19th of Kislev is celebrated by the Chabad community as the “Rosh Hashanah of Chassidism.” Farbrengens—informal gatherings at which expositions of Chassidic teaching and words of inspiration mingle with melody, dance and l’chaims—are held in every community, and chassidim wish each other a “good year in the learning of Chassidut and the ways of Chassidut.” 
The 19th of Kislev marks the day, in the year 5559 (1798), that the founder of Chabad Chassidism, Rabbi Schneur Zalman of Liadi, was released from imprisonment in Czarist Russia. Rabbi Schneur Zalman had been arrested on charges, put forth by opponents of Chassidism, that his activities, and the movement he founded, contained treasonous elements. His exoneration and release marked Chassidism’s victory over those who sought to destroy it; following the 19th of Kislev, the movement gained many new adherents, and its teachings were far more broadly and freely disseminated. Rabbi Schneur Zalman’s style of teaching also assumed a new form: he now expounded on the “soul of Torah,” previously presented only in the form of terse Kabbalistic formulas, at greater length and in a manner that more readily allowed their intellectual assimilation.
On a deeper level, the arrest and liberation were interpreted by Rabbi Schneur Zalman and his followers as the earthly speculum of a supernal drama, in which the movement itself was on trial before the Heavenly court. Is it proper to reveal the most intimate secrets of Torah, which had been the exclusive province of a select few in each generation, to the public at large? Is it proper to clothe them in garments of reason, so that these essentially supra-rational truths should take the form of a rational philosophy and creed? Rabbi Schneur Zalman’s release from earthly prison signified his vindication above: the Heavenly court had ruled that the time had indeed come for the inner light of Torah to be revealed and to illuminate the world.
The following is a freely-translated excerpt from a letter by the Rebbe to Mr. Shneur Zalman Shazar (president of the State of Israel in the years 1963-73), dated Tevet 14, 5714 (December 20, 1953), in which the Rebbe touches on the parallels between the spiritual light unleashed on Kislev 19 and modern-day lighting methods.
“It was with pleasure that I received the news that electrical power has been installed in Kfar Chabad, and that farbrengens were already held by its light on the luminous day of the 19th of Kislev. I am told that the matter was arranged thanks to your effort and vigor, and I thank you and congratulate you on this.
It is an age-old Jewish custom to seek a deeper meaning and instruction in every occurrence, as per the saying of the Mishnah, “Who is wise? He who learns from every man”; to which the Baal Shem Tov adds that one must also learn something from every event and its every detail. From the day of his redemption on the 19th of Kislev, the double  light of Rabbi Schneur Zalman of Liadi began to spread, free of all disturbances and obstructions, and in a manner that could reach also the simplest of folk. Indeed, this is the elementary principle of Chassidism: to draw down and connect the ultimate heights with the lowest depths…
The electrical force is one of the hidden forces of nature. It cannot be perceived by any of the five senses—we know of its existence only through its causations and effects. Yet this hidden force most potently banishes darkness and illuminates the night. Thus, electricity is a physical analog for the spiritual force of Chassidism, whereby the hidden element of Torah and its most arcane secrets—as revealed via Chassidic teaching and the Chassidic way of life—banish the darkness of the material world and illuminate the murkiness of the physical existence.”
 Igrot Kodesh Maharashab, vol. I, p. 259; Torat Shalom, p. 43. See also Sefer HaToldot Admor HaZaken (Kehot, 1986), pp. 731-740.
 HaYom Yom, p. 113.
 Likkutei Dibburim, vol. I, pp. 21-28. See also Sefer HaToldot Admor HaZaken, pp. 771-787.
 Torat Shalom, loc. cit.
 ] As his name indicates, Mr. Shazar was a descendant of Chabad chassidim. He maintained a close relationship with the Rebbe and greatly assisted the Chabad community and its institutions in Israel.
 Ethics of the Fathers 4:1.
 The name “Schneur” is an acronym of the Hebrew words shnei ohr (“two lights”), a reference to Rabbi Schneur Zalman of Liadi’s achievements in both the exoteric element of Torah (Halachah) and its esoteric dimension.
 Igrot Kodesh, vol. VII, pp 101-102