Kṛṣṇa describes the two stages of spiritual progress: the ‘Ārurukṣu’ (the beginner who is climbing) and the ‘Ārūḍha’ (the advanced who has reached the summit). For the beginner, active work in devotion is the ‘kāraṇam’, the necessary means to purify the mind. You cannot jump to the stage of deep, silent meditation if your mind is still full of worldly desires and agitation. You must first use your energy to serve others and the Divine. This activity acts like a scrubbing brush for the heart. Once the mind is purified and still, then ‘śamaḥ’—quiet contemplation and the cessation of outward activity—becomes the means for further progress. This provides a logical roadmap for Arjuna. He cannot skip the stage of duty (the war) to reach the stage of peace. He must work his way to silence through the fire of action. Kṛṣṇa is telling him that his current ‘work’ is actually the very ladder he needs to reach the state of meditative bliss he desires.