This verse is spoken by Dhritarashtra, the blind king of Hastinapura, who asks his charioteer Sanjaya to describe the events of the Kurukshetra war between the Pandavas and the Kauravas.
The conversation between Dhritarashtra and Sanjaya forms the framework for the teachings of the Bhagavad Gita, which is a dialogue between the warrior Arjuna and his charioteer Krishna on the battlefield of Kurukshetra.
The Bhagavad Gita is a part of the epic Mahabharata, which is one of the longest poems ever written and is considered a foundational text of Hinduism.
The Bhagavad Gita is often seen as a summary of the teachings of the Upanishads, which are a collection of ancient Hindu texts that explore the nature of reality and the self.