3:20  

कर्मणैव हि संसिद्धिमास्थिता जनकादयः ।
लोकसंग्रहमेवापि संपश्यन्कर्तुमर्हसि ॥३- २०॥

karmaNaiwa hi saMsiddhimaasthitaa janakaadayaH ।

lokasaMgrahamewaapi saMpashyankartumarhasi ॥३- २०॥

Source: Automatic ITRANS Transliteration

It was by action that Janak and others attained complete fulfillment.
With respect to the populace, as well, action is correct.

Source: Milind S. Pandit

King Janaka and others attained perfection (or Self-realization) by Karma-yoga alone. You should perform your duty (with apathetic frame of mind) with a view to guide people and for the universal welfare (of the society).

Source: The Bhagavad-Gita: The Sacred Song

Even kings like Janaka and others attained the perfectional stage by performance of prescribed duties. Therefore, just for the sake of educating the people in general, you should perform your work.

Source: Bhagavad Gita As It Is