Bhagavad Gita 1.35

एतन्न हन्तुमिच्छामि घ्नतोऽपि मधुसूदन |
अपि त्रैलोक्यराज्यस्य हेतो: किं नु मह्लिके

Translation

O Madhusudan, I do not wish to slay them, even if they attack me. If we kill the sons of Dhritarashtra, what satisfaction will we derive from the dominion over the three worlds, what to speak of this Earth?