Valmiki Ramayana Yuddha Kanda Sarga 65 Shloka 54
Original Shlokaतेदृष्टवाराक्षसश्रेष्ठंवानराःपर्वतोपमम् । वायुनुन्नाइवघनाययुस्सर्वादिशस्तदा ।।6.65.54।।
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तेवानराः those Vanaras, पर्वतोपमम् like a mountain, राक्षसश्रेष्ठम् foremost of Rakshasas, दृष्टवा seeing, तदा then, वायुनुन्नाः swept by wind, घनाःइव like clouds, सर्वाः all, दिशः directions, ययुः dispersed.
On seeing the mountain like form of the foremost of the Rakshasas. the vanaras dispersed in all directions like clouds swept by the wind.