Raavan knew that asti was the root for the Sanskrit word astitva, which meant existence. These bones, which had tenaciously refused to be consumed by the holy fire, symbolised the remnants of existence. They had to go back to the source of it all, to the Mother Goddess, in the form of the flowing, nurturing river. They would merge with the water, in the bosom of the Mother Goddess, so that even the residual bits of existence could find peace.
