The Bhagavad Gita is set within the Bhishma Parva of the Mahabharata, in the moment before battle when Arjuna sets down his bow. Across eighteen chapters and seven hundred verses, Krishna answers him — on duty, on acting without attachment to the fruit of action, and on the paths of knowledge, works, and devotion. Its ninth chapter names the leaf, the flower, the fruit, and the water that may be offered with a devoted heart.
✦ Did you know
The Bhagavad Gita is a book inside a book. It sits within the Bhishma Parva — the sixth of the Mahabharata's eighteen parvas, itself 124 chapters long.
Source: Mahabharata, Bhishma Parva