Krishna’s instruction to Arjuna on the Bhagavad Gita at the battlefield of Kurukshetra was a revival of the knowledge that he had taught long ago to Vivasvan, the Sun God. Krishna reveals this in verse 4.1 of the Bhagavad Gita: “I taught this eternal science of Yoga to the Sun-god, Vivasvan, who passed it on to Manu; and Manu in turn instructed it to Ikshvaku.” Vivasvan was the teacher of Yajnavalkya, the sage of the Shukla Yajur Veda. Thus, the disciple of Krishna was the teacher of Yajnavalkya. The connection between Krishna and Yajnavalkya through Vivasvan might be the cause of the similarities in the teachings of the Bhagavad Gita and the Isa Upanishad. There are eighteen chapters in the Bhagavad Gita, and the Isa Upanishad contains eighteen verses—devotion to Krishna is the theme of both texts.