For a sage who wishes to attain to Yoga, action is said to be the means; for the same sage who has attained to Yoga, inaction (quiescence) is said to be the means.
In simple words
Krishna explains a progression: "For someone starting out on this path, action is the way forward. For someone who has already arrived, stillness is the way forward. First you work your way up, then you rest at the top."
Word-by-word meanings
आरुरुक्षोःwishing to climbमुनेःof a Muni or sageयोगम्Yogaकर्मactionकारणम्the causeउच्यतेis saidयोगारूढस्यof one who has attained to Yogaतस्यof himएवevenशमःinaction (iescence)कारणम्the causeउच्यतेis said
Contemporary scholarly and practical interpretations for modern seekers.
Swami Sivananda
6.3 आरुरुक्षोः wishing to climb? मुनेः of a Muni or sage? योगम् Yoga? कर्म action? कारणम् the cause? उच्यते is said? योगारूढस्य of one who has attained to Yoga? तस्य of him? एव even? शमः inaction (iescence)? कारणम् the cause? उच्यते is said.Commentary For a man who cannot practise meditation for a long time and who is not able to keep his mind steady in meditation? action is a means to get himself enthroned in Yoga. Action purifies his mind and makes the mind fit for the practice of steady meditation. Action leads to steady concentration and meditation.For the sage who is enthroned in Yoga? Sama or renunciation of actions is said to be the means.The more perfectly he abstains from actions? the more steady his mind is? and the more peaceful,he is? the more easily and thoroughly does his mind get fixed in the Self. For a Brahmana there is no wealth like unto the knowledge of oneness and homogeneity (of the Self in all beings)? truthfulness? good character? steadiness? harmlessness? straightforwardness and renunciation of all actions. (Mahabharata? Santi Parva? 175.38)
Swami Chinmayananda
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
# BG 6.3
For one who seeks to ascend to the yoga of meditation, action is declared to be the first means. By performing action while renouncing the pride of authorship and attachment to results, the desires accumulated from the past are destroyed, and new desires do not arise.
To clarify the subject of attaining yoga, an apt metaphor of horsemanship is employed here. When a person first attempts to mount a spirited horse, initially the horse dominates him. If one wishes to bring a war horse under complete control, one must spend some time attempting to mount it. Placing one foot on the stirrup, holding the saddle, lifting the other foot from the ground and leaping onto the horse's back—one must make the effort to sit upon it and bring it under control. Once mounted, keeping it under control becomes easy; yet until then, the rider must pass through a state where he is neither fully seated upon the horse nor standing upon the ground.
In the beginning, we are merely doers of action, driven by ego and self-interest, we labor, we sweat, we weep, we laugh. When a person grows weary of such actions, he desires to mount the horse of mind. Such a person is called one who desires to ascend—the aspirant. That person performs action as before, yet renouncing ego and self-interest. Actions performed with the spirit of sacrifice destroy desires and purify and organize the inner instrument. Such a purified aspirant should gradually withdraw from action and practice meditation more. When he conquers the mind and brings its tendencies under his control, he is called one established in yoga. For such a yogi who has attained equanimity of mind, knowledge-born peace is the means by which he can abide in his true nature.
Thus, for one person, observing the stages of his development, two means are taught—action and meditation—which are not contradictory. In one stage, the practice of desireless action is appropriate; yet after some time, even that may sometimes disturb a person's peace and cast him down, as it were. Diluted milk made by dissolving milk powder in water nourishes a small infant, yet that bottle of milk is insufficient for a growing child who plays and works all day. He needs butter and bread. Yet that very bread could be fatal to an infant.
Similarly, in the initial stage of practice, desireless action is fitting; but for the more developed aspirant, self-reflection through deep meditation is necessary. First, action without ego is the means, and thereafter, meditation upon the nature of the Self. This practice of meditation is necessary until the aspirant firmly realizes that the pure Self alone is the ultimate truth, not the ego. Thereafter, whether he acts or does not act, he does not forget this knowledge.
Thus it is proven that actions have a definite place on the path of self-unfoldment, and likewise, the wisdom of the sages who teach this is also established.