Nefesh Hachaim is a foundational work of Jewish philosophy and mysticism written by Rabbi Chaim of Volozhin in the 19th century. The text emphasizes the importance of the soul and its connection to God, exploring how spiritual practices can elevate one's soul and enhance their relationship with the divine. The book is structured into four sections, each addressing different aspects of Jewish thought, including the nature of the soul, the significance of prayer, and the role of Torah study. Nefesh Hachaim has had a lasting impact on Jewish scholarship and is often studied in Yeshivas for its insights into spirituality and ethics.