Ramayana
ततो हते महावीर्ये वृत्रे देवभयङ्करे । ब्रह्महत्यावृतः शक्रः सञ्ज्ञां लेभे न वृत्रहा ॥ 7-86-2 ॥
Thereafter, when Vritra of great might, the terror of the gods, had been slain, Shakra (Indra), the slayer of Vritra, enveloped by the sin of brahmin-slaying, did not regain his consciousness.
english translation