Bhagavad Gita · 1.34

मातुलाः श्वशुराः पौत्राः श्यालाः सम्बन्धिनस्तथा।एतान्न हन्तुमिच्छामि घ्नतोऽपि मधुसूदन॥

mātulāḥ śhvaśhurāḥ pautrāḥ śhyālāḥ sambandhinas tathā etān na hantum ichchhāmi ghnato 'pi madhusūdana

O slayer of Madhu, I do not wish to kill them, even if they were to kill me — not even for the sovereignty of the three worlds, let alone this earth.

— Bhagavad Gita 1.34

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)