evaḿ jñātvā kṛtaḿ karma
pūrvair api mumukṣubhiḥ
kuru karmaiva tasmāt tvaḿ
pūrvaiḥ pūrvataraḿ kṛtam

Translation of Bhagavad Gita 4.15

All the liberated souls in ancient times acted with this understanding of My transcendental nature. Therefore you should perform your duty, following in their footsteps.

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

There are two classes of men. Some of them are full of polluted material things within their hearts, and some of them are materially free. Krishna consciousness is equally beneficial for both of these persons. Those who are full of dirty things can take to the line of Krishna consciousness for a gradual cleansing process, following the regulative principles of devotional service. Those who are already cleansed of the impurities may continue to act in the same Krishna consciousness so that others may follow their exemplary activities and thereby be benefited. Foolish persons or neophytes in Krishna consciousness often want to retire from activities without having knowledge of Krishna consciousness. Arjuna’s desire to retire from activities on the battlefield was not approved by the Lord. One need only know how to act. To retire from the activities of Krishna consciousness and to sit aloof making a show of Krishna consciousness is less important than actually engaging in the field of activities for the sake of Krishna. Arjuna is here advised to act in Krishna consciousness, following in the footsteps of the Lord’s previous disciples, such as the sun-god Vivasvan, as mentioned hereinbefore. The Supreme Lord knows all His past activities, as well as those of persons who acted in Krishna consciousness in the past. Therefore He recommends the acts of the sun-god, who learned this art from the Lord some millions of years before. All such students of Lord Krishna are mentioned here as past liberated persons, engaged in the discharge of duties allotted by Krishna.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

Understanding how I have acted without being bound, previously person like Janaka performed karma in order to promote it with the people.

Commentary by Sri Ramanuja of Sri Sampradaya:

4.15 Actions of the kind described above were performed even by the aspirants of old for liberation, who have become free from evil after knowing Me in this way. Therefore, after having got rid of the sins by knowledge of Me in the aforesaid way, perform actions in the same way as they were performed by those ancients like Vivasvan, Manu etc., in olden times, in the way in which their performance was taught by Me even then. I shall declare it again in what follows. Sri Krsna stresses the difficulty of undertaking the type of Karma that is going to be taught now.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Beginning from the previous four verse where Lord Krishna explains: In whatever way one worships Him then that offering He will accept. By this He refuted any conception of partiality of God and allowed Him to propound karma yoga or the performance of prescribed Vedic activities according to status and position in life. Thus knowing that actions performed without egoism do not bind one to material nature. Ancient seekers of moksa or liberation such as King Janaka the father of Sita who performed great deeds of yore for the benefit of the world and for purification of their minds. Therefore Lord Krishna is encouraging Arjuna to follow in their footsteps.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Even after realising the eternally, transcendental position of the Supreme Lord one should still perform Vedic actions as a matter of principle following the tradition of the ancients. The performance of Vedic actions of the ancients means without desires or attachments.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

So Lord Krishna sums up His conclusion for this theme by stating that having known that He is completely free from desire and attachment although performing such magnificent activities like creation of all the worlds He is never implicated by it. But great beings like Manu and Janaka performed actions according to the injunctions of the Vedic scriptures and being free from egoism without desire for rewards also achieved moksa or liberation as such actions are never binding. Therefore Arjuna and anyone else should perform such actions following in their footsteps as they have come down through the ages in parampara or diciplic succession.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

4.15 Jnatva, having known; evam, thus, that ‘I am not an agent; I have no desire for the results of actions’; karma, duties; krtam, were undertaken; api, even; purvaih, by the ancient; mumuksubhih, seekers of Liberation. Tasmat, therefore; tvam, you; kuru, undertake; karma, action; eva, itself. You ought not to sit quietly, or even renounce. Therefore, you (undertake actions) because they were performed by the ancients as well-if you have no Self-knowledge, then (undertake actions) for self-purification; or, if you have Self-knowledge, then (undertake actions) in order to prevent people from going astray-, as were krtam, performed; purvataram, earlier; purvaih, by the ancient ones, Janaka and others; not actions as are undertaken in the present day. [This last portion of the sentence is translated by some as follows: You should not undertake actions which are done in the present manner (i.e. do not perform actions in the manner undertakne by people nowadays, which neither purifies the mind nor helps people). (See G1. Pr. p. 114.) ‘If action has to be undertaken here, then I shall do so following Your instruction itself. What is the use of specifying that it was done earlier by the ancient ones?’ ‘The answer is: Because there is a great difficult as regards actions.’ How?

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

4.15 Evam etc. Therefore being purified by this [sort of] conviction you too should perform actions that are to be necessarily performed. But, if it is said that success would result just from the non-performance of action, that is not correct. For –

Sanskrit Shloka Without Transliteration Marks:

evam jñatva krtam karma
purvair api mumuksubhih
kuru karmaiva tasmat tvam
purvaih purva-taram krtam

Sanskrit to English Word for Word Meanings:

evam — thus; jñātvā — knowing well; kṛtam — was performed; karma — work; pūrvaiḥ — by past authorities; api — indeed; mumukṣubhiḥ — who attained liberation; kuru — just perform; karma — prescribed duty; eva — certainly; tasmāt — therefore; tvam — you; pūrvaiḥ — by the predecessors; pūrva-taram — in ancient times; kṛtam — as performed.