B.G 4.01, 02, and 03

श्रीभगवानुवाच
इमं विवस्वते योगं प्रोक्तवानहमव्ययम्। विवस्वान्मनवे प्राह मनुरिक्ष्वाकवेब्रवीत् ॥१॥

śrībhagavānuvāca
imaṁ vivasvatē yōgaṁ prōktavānahamavyayam। vivasvānmanavē prāha manurikṣvākavēbravīt ॥1॥

[श्री भगवान् उवाच
इमं विवस्वते योगं प्रोक्तवान् अहम् अव्ययम्। विवस्वान् मनवे प्राह मनुः इक्ष्वाकवेः अब्रवीत्॥
śrī = glorious; bhagavān = the Lord; uvāca = said; imaṁ = this; vivasvatē = to Sun; yōgaṁ = The Yōga; prōktavān = was spoken; aham = by me; avyayam = eternal/imperishable;। vivasvān = The Sun; manavē = to Manu; prāha = spoke; manuḥ = Manu to; ikṣvākavēḥ = Ikshwaku; abravīt = narrated it;॥]

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॥

ēvaṁ paramparāprāptamimaṁ rājarṣayō viduḥ। sa kālēnēha mahatā yōgō naṣṭaḥ parantapa ॥2॥

[एवं परम्परा प्राप्तम् इमं राजर्षयो विदुः। स कालेन इह महता योगो नष्टः परन्तप॥
ēvaṁ = thus; paramparā = in disciple succession; prāptam = received; imaṁ = this; rājarṣayō = royal sages; viduḥ = the knowledge;। sa = that; kālēna = with passage of time; iha = this; mahatā = the great; yōgō = the Yōga; naṣṭaḥ = was lost; parantapa = O Arjuna, scorcher of foes;॥]

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॥

sa ēvāyaṁ mayā tē'dya yōgaḥ prōktaḥ purātanaḥ। bhaktō'si mē sakhā cēti rahasyaṁ hyētaduttamam ॥3॥

[स एव अयं मया ते अद्य योगः प्रोक्तः पुरातनः। भक्तो असि मे सखा च इति रहस्यं हि एतत् उत्तमम्॥
sa = that; ēva = even; ayaṁ = this; mayā = by me; tē = to you; adya = today; yōgaḥ = the Yōga; prōktaḥ = has been spoken; purātanaḥ = the ancient;। bhaktō = a devotee; asi = are; mē = my; sakhā = friend; ca = and; iti = thus; rahasyaṁ = secret; hi = indeed; ētat = this; uttamam = highest;॥]

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।

buddhēḥ parasya māhātmyaṁ, karmabhēdaḥ, jñānamāhātmyaṁ ca ucyatē asminnadhyāyē।

[buddhēḥ = understanding of; parasya = of the Supreme; māhātmyaṁ = greatness; karmabhēdaḥ = differentiation of action/duties; jñānamāhātmyaṁ = greatness of knowledge; ca = and; ucyatē = is narrated; asminnadhyāyē = in this chapter;।]

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॥

pūrvānuṣṭhitaścāyaṁ dharmaḥ ityāha - imam iti ॥1-3॥

[pūrvānuṣṭhitaścāyaṁ = previously practiced, and, this; dharmaḥ = DHARMA; ityāha = is said so; - imam iti = by the 'imam' verse;॥1-3॥]

Previously also DHARMA was practiced is indicated by 'imam' verse.