Most people who perform Pitru Tarpan or light a lamp on Mahalaya believe they are settling the oldest debt a human being can carry. They are settling one of three. The Taittiriya Samhita and later the Manusmriti name the Tri-Rna, three debts that precede every choice, every relationship, every act of worship a person will ever make. Ignoring two of them while honouring the third is a little like repaying one creditor and calling yourself debt-free.
