CHAPTER 4 · VERSE 2
Bhagavad Gita 4.2
एवं परम्पराप्राप्तमिमं राजर्षयो विदुः। स कालेनेह महता योगा नष्टः परन्तप॥
Thus passed down through the disciplic succession, the saintly kings understood it. But with the long passage of time, O scorcher of enemies, this Yoga was lost to the world.
Explains how divine knowledge becomes diluted or lost over time when disconnected from authentic lineages.