Hindus believe that Sri Krishna lived on earth around 5000 years ago. The earliest textual reference or mention of Sri Krishna in a Hindu scripture is found in the Vedas. Vishnu or Krishna is described as cowherd in Rig Veda. The reference to Krishna is found in Rig Veda 1.22.18.
Krishna as cowherd has hidden symbolism. The belief is that cow symbolically represents Mother Earth and Krishna appears to protect the earth from Adharma.
Chandogya Upanishad, the famous text embedded in the Chandogya Brahmana of the Sama Veda of Hinduism, refers to Krishna as the son of Devaki.
Aitareya Aranyaka, which belongs to the Shakala recension of the Rig Veda, mentions Krishna as a member of the Vrishni clan.
Vrishnis were an ancient Vedic clan who were the descendants of Vrishni, a descendant of Yadu. It is believed that Vrishni was son of Satvata, a descendant of Yadu, the son of Yayati. He had two wives, Gandhari and Madri. He has a son named Devamidhusha by his wife Madri. Vasudeva, the father of Krishna was the grandson of Devamidhusha.
Other popular reference of Krishna is found in the book of grammar of Panini. He refers to the incidents in the life of Krishna. Panini is believed to have lived between the 6th and 5th Century BC.
Hathibada Ghosundi Inscriptions, sometimes referred simply as the Ghosundi Inscription or the Hathibada Inscription, in Rajasthan belongs to the 2nd Century BC in Brahmi and Sanskrit script refer to the worship of Vasudeva and his brother Samkarshana.
The name of Krishna is also found in the 1st century BC Mora Stone slab in Mathura.