इमं विवस्वते योगं प्रोक्तवानहमव्ययम्।विवस्वान् मनवे प्राह मनुरिक्ष्वाकवेऽब्रवीत्॥
imaṃ vivasvate yogaṃ proktavān aham avyayamvivasvān manave prāha manur ikṣvākave ’bravīt
Word by word
The verse says
Krishna said: I taught this unfading practice to the sun. The sun told Manu. Manu told Ikshvaku.
In plain words
A new chapter, and it opens by handing you a chain of names.
Krishna taught the sun. The sun taught the first man. The first man taught the first king.
What Arjuna has been hearing for two chapters turns out not to be new. It is being returned to circulation.
Where you've felt this · in study
A technique your grandmother used, which she got from someone whose name nobody remembers. You use it without thinking. It is older than everyone who has ever used it.
Going deeper
The chapter opens with lineage, and the placement is doing work.
Chapter 3 ended inside a single person's head — desire hiding in the faculties, the self steadying itself. Chapter 4 immediately widens to cosmic time and a chain of teachers.
Avyayam — unfading, not wearing out. It is the same root as the akṣara of 3.15. What is being transmitted does not degrade in transmission, which is a strong claim about the thing rather than about the teachers.
And notice the first recipient: the sun. Not a sage. The Gita's chain starts outside the human world and comes down into it — sun, then the first man, then the first king. Knowledge arriving from above and entering history at the point where someone has to govern.
That descent matters for a chapter that is about to define avatāra. The pattern of something higher coming down into the ordinary is stated about a teaching before it is stated about a person.