The Bhagavad Gita is technically part of
Book 6 of the Mahabharata, although it is
known to be a later accretion to the saga, which stands on its own merits.
It is a dialog between the God Krishna and the hero Arjuna,
taking place in a timeless moment on the battlefield
before the climactic struggle between good and evil.
The Gita (which can be found in hotel bedstands throughout India)
is a classic summary of the core beliefs of Hinduism.
It has had a significant influence far beyond Hinduism.
Robert Oppenheimer apocryphically recited
the verse (from Chapter 11)
'I [have become] Death, Destroyer of Worlds",
just before the first test of the atom bomb,
which ironically has a much different meaning in context.
This has now been cross-referenced with the
Sanskrit text.
