Bhagavad Gita, Chapter 10, Verse 12-13

Arjuna said: The Supreme Brahman, the Supreme Abode, the Supreme Purifier, are You. All the Rishis, the Deva-Rishi Nârada as well as Asita, Devala and Vyâsa have declared You as the Eternal, the Self-luminous Purusha, the first Deva, Birth-less and All-pervading. So also You Yourself say to me.

Arjun backs his own real conviction with real testimony from sages who said the same thing long before him, and points out that this isn't a new idea being introduced for the first time.

This isn't a lone claim, it's shown resting on a lineage of independent voices already on record. Real credibility here comes from agreement across multiple honest witnesses, not from one person's word alone, real consistency across sources is treated as meaningful, not coincidental.