Knowing this, even the ancient seekers of liberation performed action. So you too should simply act, as those before you did in earlier times.
Explanation
Krishna has just said that actions do not bind him because he has no craving for their results. Here he tells Arjuna that earlier seekers of liberation (mumukṣu) understood this and still acted, so Arjuna should do his own action (karma) too. Traditions stress different points: Advaita readers see action done with knowledge as purifying the mind, while devotional and karma-yoga readings see action itself as the path.