B.G 4.01, 02, and 03
श्रीभगवानुवाच
इमं विवस्वते योगं प्रोक्तवानहमव्ययम्। विवस्वान्मनवे प्राह मनुरिक्ष्वाकवेब्रवीत् ॥१॥
Sri Bhagavān said:
I shared this eternal and undying Yōga with the Sun. He taught it to his son Manu, and Manu narrated it to Iksvaku.
एवं परम्पराप्राप्तमिमं राजर्षयो विदुः। स कालेनेह महता योगो नष्टः परन्तप ॥२॥
Thus, the knowledge was passed down through the disciple succession of royal kings. But, O Scorcher of foes, as time passed, this magnificent Yōga was lost.
स एवायं मया तेऽद्य योगः प्रोक्तः पुरातनः। भक्तोऽसि मे सखा चेति रहस्यं ह्येतदुत्तमम् ॥३॥
Because you are both my dear friend and a devoted student, I have shared that same secret supreme knowledge, the ancient Yōga, to you.
Gīta Bhāshya 4.01-03
This chapter delves into the immense significance of the Supreme, the process of distinguishing actions, and the crucial role of knowledge. This verse provides evidence that the knowledge to be shared was prevalent in the past as well.
बुद्धेः परस्य माहात्म्यं, कर्मभेदः, ज्ञानमाहात्म्यं च उच्यते अस्मिन्नध्याये।
Understanding of the greatness of Supreme, how to differentiate the duties, and the greatness of knowledge are narrated in this chapter.
पूर्वानुष्ठितश्चायं धर्मः इत्याह - इमम् इति ॥१-३॥
Previously also DHARMA was practiced is indicated by 'imam' verse.