Bhagavad Gita 1.36

निहत्य धार्तराष्ट्रान्नः का प्रीतिः स्याज्जनार्दन।पापमेवाश्रयेदस्मान्हत्वैतानाततायिनः ॥१.३६॥

nihatya dhārtarāṣṭrānnaḥ kā prītiḥ syājjanārdanapāpamevāśrayedasmānhatvaitānātatāyinaḥ

By killing these sons of Dhritarashtra, what pleasure could be ours, O Janardana? Only sin would accrue to us from killing these felons.

गीता