evaḿ paramparā-prāptam
imaḿ rājarṣayo viduḥ
sa kāleneha mahatā
yogo naṣṭaḥ parantapa

Translation of Bhagavad Gita 4.2

This supreme science was thus received through the chain of disciplic succession, and the saintly kings understood it in that way. But in course of time the succession was broken, and therefore the science as it is appears to be lost.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

It is clearly stated that the Gita was especially meant for the saintly kings because they were to execute its purpose in ruling over the citizens. Certainly Bhagavad-gita was never meant for the demonic persons, who would dissipate its value for no one’s benefit and would devise all types of interpretations according to personal whims. As soon as the original purpose was scattered by the motives of the unscrupulous commentators, there arose the need to reestablish the disciplic succession. Five thousand years ago it was detected by the Lord Himself that the disciplic succession was broken, and therefore He declared that the purpose of the Gita appeared to be lost. In the same way, at the present moment also there are so many editions of the Gita (especially in English), but almost all of them are not according to authorized disciplic succession. There are innumerable interpretations rendered by different mundane scholars, but almost all of them do not accept the Supreme Personality of Godhead, Krishna, although they make a good business on the words of Sri Krishna. This spirit is demonic, because demons do not believe in God but simply enjoy the property of the Supreme. Since there is a great need of an edition of the Gita in English, as it is received by the parampara (disciplic succession) system, an attempt is made herewith to fulfill this great want. Bhagavad-gita—accepted as it is—is a great boon to humanity; but if it is accepted as a treatise of philosophical speculations, it is simply a waste of time.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

No commentary by Sri Visvanatha Cakravarti Thakur.

Commentary by Sri Ramanuja of Sri Sampradaya:

4.1 – 4.2 The Lord said — This Karma Yoga declared to you should not be considered as having been taught now merely, for creating encouragement in you for war. I Myself had taught this Yoga to Vivasvan at the commencement of Manu’s age as a means for all beings to attain release, which is man’s supreme end. Vivasvan taught it to Manu, and Manu to Iksvaku. The royal sages of old knew this Yoga transmitted by tradition. Because of long lapse of time and because of the dullness of the intellect of those who heard it, it has been almost lost.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

This eternal yoga or the science of the individual consciousness attaining communion with the ultimate consciousness. The saintly kings such as King Nimi as well as royal sages at court all were knowledgeable of this yoga as instructed by their ancestors Ishvaktu and others. The reason why the kings of the day were not knowledgeable of this yoga was because it was lost to parampara or authorised disciplic succession due to great passage of time.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Sri Madhvacharya did not comment on this sloka.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

Thus was transmitted from Lord Krishna a distinguished parampara or disciplic succession from illustrious father to illustrious son. This knowledge was passed onto the saintly kings and royal sages like Nimi and Sagara; but its origins are without beginning because its roots are in the eternal Vedas. By great efflux of time and degradation of human intelligence limiting qualified recipients this great knowledge disappeared into oblivion due to a break in parampara causing a discontinuation of the tradition in this world.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

4.2 Rajarsayah, the king-sages, those who were kings and sages (at the same time); viduh, knew; imam, this Yoga; which was evam parampara-praptam, received thus through a regular succession of Ksatriyas. Sah, that; yogah, Yoga; nastah, is lost, has go its traditional line snapped; iha, now; mahata kalena, owing to a long lapse of time. parantapa, O destroyer of foes. By para are meant those against oneself. He who, like the sun, ‘scorches’ (tapayati) them by the ‘rays’ of the ‘heat’ of his prowess is parantapa, i.e. scorcher of antagonists. Noticing that the Yoga has got lost by reaching people who are weak and have no control of their organs, and that the world has become associated with goals that do not lead to Liberation,

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

4.1 See Comment under 4.3

Sanskrit Shloka Without Transliteration Marks:

evam parampara-praptam
imam rajarsayo viduh
sa kaleneha mahata
yogo nastah parantapa

Sanskrit to English Word for Word Meanings:

evam — thus; paramparā — by disciplic succession; prāptam — received; imam — this science; rāja-ṛṣayaḥ — the saintly kings; viduḥ — understood; saḥ — that knowledge; kālena — in the course of time; iha — in this world; mahatā — great; yogaḥ — the science of one’s relationship with the Supreme; naṣṭaḥ — scattered; parantapa — O Arjuna, subduer of the enemies.