Valmiki Ramayana Yuddha Kanda Sarga 52 Shloka 35
Original Shlokaताडितःसतयातत्रगदयाभीमरूपया । सकपिर्मारुतबलस्तंप्रहारमचिन्तयन् ।।6.52.35।। धूम्राक्षस्यशिरोमध्येगिरिशृङ्गमपातयत् ।
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तत्र there, भीमवेरूपया of fierce form, तया like that, गदया mace, ताडितः fell, सः he, मारुतबलः equal to WindGod in strength, सःकपिः that monkey, तम् that, प्रहारम् hurt, अचिन्तयन् without caring, धूम्राक्षस्य Dhumraksha's, शिरोमध्ये middle of the head, गिरिशृङ्गम् peak of the mountain, अपातयत् dropped.
That fierce mace fell on Hanuman's head. Hanuman who was equal to wind god without caring for the hit dropped the peak of the mountain on the centre of Dhumraksha's head.