One who contributes from his wealth for the purpose of writing or publishing a sefer of a Tzaddik –
Behold, at any given time, and in any corner of the world, that a person studies from this sefer, the Tzaddik [on high] evokes merit on behalf of the donor through whom the sefer was disseminated.
—The Rebbe, Igrot Kodesh, vol 2
by Rabbi Avraham Dovid Lavut
Shaar Hakollel is the earliest and most definitive work on the Siddur of the Alter Rebbe, R. Schneur Zalman of Liadi.
Authored by the Rebbe’s great-grandfather, Rabbi Avraham Dovid Lavut, it explores the halachic rulings and customs established by the Alter Rebbe in his Siddur and why they sometime differ from the rulings in his Shulchan Aruch, and presents copious sources and annotations to the Siddur.
Shaar Hakollel is an indispensable guide to understanding the structure of the Alter Rebbe’s Siddur and the Chabad customs derived therefrom.