Tanya/Iggeres HaKodesh - The Holy Epistle...

The Tanya, also known as Iggeres HaKodesh, is a foundational text of Chabad Hasidism authored by Rabbi Schneur Zalman of Liadi. It distills four millennia of Jewish wisdom into answers for personal and existential questions about God, the soul, and humanity's place in the world.

The work has influenced Jewish thought by offering a systematic approach to these topics and remains a central study text in Hasidic communities.