Gavin D. Flood

“The origin of the doctrines of karma and samsara are obscure. These concepts were certainly circulating among the Sramanas, and Jainism and Buddhism developed specific and sophisticated ideas about the process of transmigration. It is very possible that karma and reincarnation entered mainstream brahmanical thought from the s§ramana or renouncer traditions. Yet on the other hand, although there is no clear doctrine of transmigration in the vedic hymns, there is the idea of ‘redeath’: that a person, having died in this world, might die yet again in the next. Ritual procedures are meant to prevent this eventuality. From the notion of redeath the idea of a return to this world could have developed. We also have in the Rg Veda the idea that different parts of a person go to different places upon death: the eyes go to the sun, the breath (atman) to the wind, and the essential ‘person’ to the ancestors. Rebirth into this world could have developed from this partite view of a person.”
― Gavin D. Flood, An Introduction to Hinduism