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
"Or Hatorah al Siddur (Tefillah)” contains the Tzemach Tzedek’s discourses and elucidations on the text of the prayers and on the expositions of his grandfather, Rabbi Schneur Zalman of Liadi, in his “Siddur with Chasidic Commentary.” Collected largely from copyist’s manuscripts, with some from the Tzemach Tzedek’s actual handwriting, this volume explains weekday, Shabbat, and High Holiday prayers, with a large section discussing the marriage blessings. A supplemental list directs the reader to where further commentary on the prayers can be found throughout the rest of the Or Hatorah series.