Valmiki Ramayana Yuddha Kanda Sarga 83 Shloka 29

परन्तप scorcher of enemies!, धर्मोवा if dharma alone, अधर्मोवा or adharma, भूतःpresent, भवेद्यदि and in future, वज्रीIndra, शतक्रतुः a hundred sacrifices, मुनिम् sage, हत्वा killing, इज्याम् sacrifice, न स्मकुर्यात् not performed

"Indra killed an ascetic (Viswarupa) and did fire sacrifice. If dharma alone is his duty, he could have done hundreds of fire sacrifices and not have killed the ascetic. If adharma is duty he would have killed the ascetic and not done fire sacrifice."