Valmiki Ramayana Yuddha Kanda Sarga 59 Shloka 92
Original Shlokaविसंज्ञंवानरंदृष्टवादशग्रीवोरणोत्सुकः । रथेनाम्बुदनादेनसौमित्रिमभिदुद्रुवे ।।6.59.92।।
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दशग्रीवः ten headed, वानरम् at the Vanaras, विसंज्ञम् unconscious, दृष्टवा watching, रणोत्सुकः eager to fight, अम्बुदनादेन resembling the rattling sound of cloud, रथेन chariot, सौमित्रिम् to Saumithri, अभिदुद्रुवे went towards.
Finding the vanara unconscious the ten headed Ravana who was eager to fight went towards Saumithri in the chariot making sounds that resembled the sound of rattling of clouds.