Bhagavad Gita, Chapter 4, Verse 1

I told this imperishable Yoga to Vivasvat; Vivasvat told it to Manu; and Manu told it to Ikshvâku.

This teaching didn't start today, it's been passed down a long real chain before it ever reached Arjuna.

Krishna opens this chapter by tracing where the knowledge actually comes from, not something newly invented, but something handed down through a real lineage. That history is what gives the teaching its weight.