B.G 4.15

एवं ज्ञात्वा कृतं कर्म पूर्वैरपि मुमुक्षुभिः। कुरु कर्मैव तस्मात्त्वं पूर्वैः पूर्वतरं कृतम् ॥१५॥

evaṁ jñātvā kr̥taṁ karma pūrvairapi mumukṣubhiḥ। kuru karmaiva tasmāttvaṁ pūrvaiḥ pūrvataraṁ kr̥tam ॥15॥

[एवं ज्ञात्वा कृतं कर्म पूर्वैः अपि मुमुक्षुभिः। कुरु कर्म एव तस्मात् त्वं पूर्वैः पूर्वतरं कृतम्॥
evaṁ = thus; jñātvā = knowing; kr̥taṁ = done; karma = actions; pūrvaiḥ = by previous; api = also/even; mumukṣubhiḥ = seekers of liberation;। kuru = perform; karma = action; eva = only; tasmāt = therefore; tvaṁ = you; pūrvaiḥ = by previous / by ancestors; pūrvataraṁ = pocessing the similar attitude as previous; kr̥tam = done;॥]

(Understanding Me) thus, knowing the actions done by previous seekers of liberation, you also perform such actions only, possessing the similar attitude as previously possessed by your ancestors.

Gīta Bhāshya 4.15

The know-how of how to get liberated already exists in the tradition. Just follow the conduct of your ancestors.

एवं ज्ञात्वाऽपि कर्मकरणे आचारोऽप्यस्तीत्याह - एवं इति। पूर्वतरं कर्म पूर्वभावी इत्यर्थः ॥१५॥

evaṁ jñātvā'pi karmakaraṇe ācāro'pyastītyāha - evaṁ iti। pūrvataraṁ karma pūrvabhāvī ityarthaḥ ॥15॥

[evaṁ = thus; jñātvā'pi = having known, even; karmakaraṇe = in the performance of action; ācāro'pyastītyāha = conduct also, exists, it is said; evaṁ iti = through "evaṁ" verse;। pūrvataraṁ karma = "pūrvataraṁ karma"; pūrvabhāvī = possessing the similar attitude as previous ancestors; ityarthaḥ = is the meaning;]

There already exists a traditional conduct that is aware of how to perform the actions, is conveyed by "evaṁ" verse. "pūrvataraṁ karma" means "possessing the similar attitude as previous ancestors".