Ramayana
तस्माद्दण्डे महाबाहो यत्नवान्भव पुत्रक । धर्मो हि परमो लोके कुर्वतस्ते भविष्यति ॥ 7-79-10 ॥
Therefore, O mighty-armed son, be diligent in the matter of punishment; for as you act thus, the highest righteousness in the world shall be yours."
english translation