Valmiki Ramayana Yuddha Kanda Sarga 66 Shloka 3
Original Shlokaतमवध्यंमघवतायमेनवरुणेनवा । प्रेक्ष्यभीमाक्षमायान्तंवानराविप्रदुद्रुवुः ।।6.66.3।।
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मघवता by Indra, यमेनby Yama, वरुणेनवा or even Varuna, अवध्यम् not be killed, भीमाक्षम् with frightening eyes, तम् him, प्रेक्ष्य observing, वानराः the Vanaras, विप्रदुद्रुवुः ran in fear.
Observing that rakshasa with frightening eyes, who could not be killed by Indra or Yama or even by Varuna coming towards them the vanaras ran in fear.