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
Tract on Prayer
by Rabbi Shalom DovBer Schneersohn of Lubavitch
Tract on Prayer clarifies how to prepare for prayer, explaining the role and dynamics of contemplation before and during prayer.
The Tract on Prayer is, in the words of Rabbi Sholom Dov Ber's son and successor, Rabbi Yosef Yitzchak Shneersohn, "a definitive guide to finding a balm and remedy for the maladies of the soul, and to developing one's faculties and abilities through genuine service."