Valmiki Ramayana Aranya Kanda Sarga 44 Shloka 20
Original Shlokaतेन मर्मणि निर्विद्धं शरेणानुपमेन हि। मृगरूपं तु तत्त्यक्त्वा राक्षसं रूपमास्थितः।।3.44.20।। चक्रे स सुमहाकायं मारीचो जीवितं त्यजन्।
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सः मारीचः that, Maricha, तेन by that, अनुपमेन matchless, शरेण by the dart, मर्मणि in vital part, निर्विद्धम् struck, तत् then, मृगरूपम् form of a deer, त्वक्त्वा giving up, राक्षसं रूपम् form of a demon, आस्थितः assumed, जीवितम् life, त्यजन् while giving up, सुमहाकायम् that huge body, चक्रे attained.
Struck in the vital part by Rama's matchless dart, Maricha gave up the form of the deer and assumed his huge body of the demon.