Bhagavad Gita Chapter 3, Verse 41

तस्मात्त्वमिन्द्रियाण्यादौ नियम्य भरतर्षभ | पाप्मानं प्रजहि ह्येनं ज्ञानविज्ञाननाशनम् ||

tasmāt tvam indriyāṇy ādau niyamya bharatarṣabha pāpmānaṁ prajahi hy enaṁ jñāna-vijñāna-nāśanam

Therefore, O best of the Bharatas, control the senses first, and then slay this sinful destroyer of knowledge and realization.

After exposing desire (kāma) as the enemy, Krishna gives the battle plan: 'Tasmāt'—therefore—control senses FIRST (indriyāṇy ādau niyamya). Not morality. Strategy. Why first? Senses are desire's entry point (verse 3.40). Your eyes see → desire arises. Block the gateway, starve the enemy. Then: 'prajahi pāpmānam'—slay this destroyer. What does it destroy? 'Jñāna-vijñāna-nāśanam'—your knowledge and realization. You KNOW better, but desire clouds judgment. The method: control upstream (senses), victory downstream (desire) follows.