Jewish mourning custom draws on the layered soul the Kabbalistic sources describe, and Ruach, the moral and emotional soul, is held by some authorities to take longer than Nefesh to settle after death, its departure tied to the resolution of a person's emotional and ethical conduct in life rather than to the body's decay alone. Where Nefesh is bound to appetite, Ruach carries a person's character in the fuller sense, and its state after death is described in some sources as shaped by how that character was lived out, an idea that stands behind the traditional emphasis on eulogy and honest reckoning with a life at a Jewish funeral.
Some later ethical and Hasidic writers describe acts of charity and study undertaken in a deceased relative's name as work that can elevate the departed's Ruach specifically, refining the moral and emotional soul in a way distinct from the more bodily elevation associated with Nefesh.
This practical use, tied to mourning and remembrance, runs alongside Ruach's more abstract place in Kabbalistic cosmology, where it corresponds to the second of the Four Worlds; the funerary application treats a cosmological doctrine as something the living can act on for the sake of the dead, rather than only a description of the soul's structure.