Ramayana
यो हि शत्रुं समुत्पाट्य पार्थिवस्य पुनः क्षये । न विधत्ते नृपं तत्र नरकं स हि गच्छति ॥ 7-62-18 ॥
"For he who, having uprooted an enemy, does not, upon the fall of that king's realm, install a ruler there, surely goes to hell."
english translation