Shaarei Avodah, foundations of worship of G-d according to Kabbalah and Chabad Chassidic teachings, by Rebbe Aharon HaLevi Segal Horowitz of Starosel'ye. Shklow, [1821]. First edition.
Title page states: "Shaarei Avodah, named the Worship of Average Men - composed and established by the Rebbe… Aharon HaLevi… based on the foundations of worship which he received from his teacher… R. Shneur Zalman… and based on golden foundations of the Zohar and the writings of the Arizal". The book endeavors to explain the fundamentals of Chabad's approach to worship of G-d, based on the principles of the Arizal's doctrine, as the author absorbed and understood from the teachings of his prime teacher, the Baal HaTanya.
Rebbe Aharon HaLevi Segal Horowitz (1766?-1829), G-dly kabbalist, outstanding and profound Torah scholar. A leading and close disciple of the Baal HaTanya. From the age of 17, he did not part from his teacher, and became his confidant and close attendant. During most of his teacher's tenure as rebbe, he was the close friend of the Rebbe's son, R. Dov Ber, the Mitteler Rebbe of Lubavitch. They together offered guidance in worship of G-d to the young men who frequented the Rebbe's court, and both wrote letters to the Chassidim in matters of service of G-d. When the Baal HaTanya moved to Liadi in 1802, he followed him there, to remain close to his teacher. The conflict between him and the Mitteler Rebbe began ca. 1809, for various reasons, together with a certain tension between him and his teacher, the Baal HaTanya, which caused him to return to his hometown Osweya. His teacher was deeply sorrowed by his departure, exclaiming "One of my eyes was excised". After the passing of the Baal HaTanya in 1813, a fierce controversy erupted between R. Aharon and the Mitteler Rebbe, regarding the spiritual heritage of the Baal HaTanya, an intellectual debate in profound topics of service of G-d according to the Chabad doctrine. Letters, booklets and books were written and printed on both sides, in which each one exposes his method and approach, and criticizes the opponent's approach. Thus, two courts following the teachings of the Baal HaTanya developed. R. Aharon served as rebbe in Starosel'ye, whilst the Mitteler Rebbe served as Rebbe in Lubavitch. Several of the Baal HaTanya's foremost disciples adopted the path of R. Aharon, headed by R. Avraham Sheines, son-in-law of the Baal HaTanya. In 1820, R. Aharon published in Shklow his first composition - Shaarei HaYichud VehaEmunah, in which he explains the Arizal's doctrine based on the teachings of the Baal HaTanya. That book begins with an important preface, which served as a basis for investigating the nature of the Baal HaTanya's school of thought.
This book, Shaarei Avodah, is the second book published in his lifetime, and consists of explanations of the fundamentals of worship of G-d according to teachings of the Arizal and the Baal HaTanya, as he understood them. In his preface to this book, he contests the approach of the Mitteler Rebbe. After his passing, his books Avodat HaLevi on the Torah and Festivals were published, including in-depth halachic responsa he replied to queries sent to him.
[20], 12, 17-49; 52; 70; 60; 22 leaves. Leaves [12]-[15] of first sequence appear twice. 16.5 cm. Light-colored, thick high-quality paper. Good condition. Stains. Dark stains to a few leaves. Tear to title page, affecting several letters and ornament on verso, repaired with paper and handwritten replacement. Tears to several leaves, close to and slightly affecting text. Original leather binding. Minor damage to binding.
Handwritten notes by Professor Gershom Scholem appear on the front endpaper, opposite the title page.
Stefansky Chassidut, no. 589.

Kuntres Perush HaMilot, called Mahadura Batra – commentary and expansion of the siddur of the Baal HaTanya, by his son Rebbe Dov Ber Shneuri of Lubavitch, the "Mitteler Rebbe". Warsaw, 1867. First edition.
Two title pages, the first brief and the second more detailed. Blue front wrapper, on which an abbreviated version of the title page is printed.
In 1816, the Mitteler Rebbe printed in Kopust a year-round siddur, with kabbalistic and Chassidic explanations of the words of the prayers, which he heard from his father, the Baal HaTanya, on Friday nights and which he later wrote. The explanations of the Baal HaTanya were said in a relatively brief manner and did not cover the entire siddur, only large sections therein. On the second title page of this book it is written: "Since the explanations were originally cited briefly, in his later years Rebbe Dov Ber added strength… to rewrite the explanations which were said in the past…". The book is called Mahadura Batra because it contains elucidation and expansion of explanations which had already been printed briefly in the Kopust siddur, which could be considered the Mahadura Kama. Most of this book, indeed, elucidates and expands upon that which had already been printed in the past. However, part of the book contains new explanations, on the parts of the siddur which the Baal HaTanya did not reach, and these are novellae of his son, the author (Chapters 128-137; 152-166).
In their approbation, the rabbis of Vitebsk attest that the Rebbe, the author, "was very fond of these booklets and often praised them, as I myself heard from his holy mouth".
[1] printed front wrapper, [2], 114 leaves. 24 cm. Good condition. Stains. Minor wear to several leaves. Tear to wrapper (almost without loss). Small wormholes to wrapper, first leaves and last leaf. New leather binding.
Stefansky Chassidut, no. 474.