Vedic background
Shraddha rests on the Vedic belief that ancestors inhabit Pitru Loka and require sustenance from their descendants' offerings. The Garuda Purana says that an unperformed or incorrectly-timed Shraddha creates pitru dosha — ancestral karmic residue that can manifest as family strife, health issues, or blocked fertility. For families without the means for a full ritual, even simple tarpan with water and black sesame at home, performed with attention, is considered valid.