Valmiki Ramayana Yuddha Kanda Sarga 67 Shloka 158
Original Shlokaस तस्यबाहुर्गिरिशृङ्गकल्पःसमुद्गरोराघवबाणकृत्तः । पपाततस्मिन् हरिराजसैन्येजघानतांवानरवाहिनीं ।।6.17.158।।
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गिरिशृङ्गकल्पः mountain peak, समुद्गरः that mace, राघवबाणकृत्तः by Raghava's arrow, सः he, तस्यबाहुः his arm, तस्मिन् by this, हरिराजसैन्ये monkey king's army, पपात fell, ताम् them, हरिवाहिनीं च Vanara army too, जघान killed.
Kumbhakarna's arm severed by Rama's arrow was like a mountain peak. It fell on Vanara army too and killed the monkey king's army.