In the BrhadaranyakaUpanishad, one of the oldest Upanishads, one of the teacher Yajnavalkya's interviewers.
The third chapter of this upanishad introduces a succession
of interrogators, each attempting to put Yajnavalkya's claim that he is the
finest brahmin of all time to the test.
Yajnavalkya is ultimately questioned by Artabhaga regarding
the human sense faculties and their regions of operation, and what happens to a
person after death.
In what is often considered as the first mention to this
essential Indian religious concept, Yajnavalkya takes him aside in secret and
explains to him about karma ("activity").
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