Valmiki Ramayana Sundara Kanda Sarga 3 Shloka 28
Original Shlokaअहं राक्षसराजस्य रावणस्य महात्मनः। आज्ञाप्रतीक्षा दुर्धर्षा रक्षामि नगरीमिमाम्।।5.3.28।।
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राक्षसराजस्य demon king's, महात्मनः of the great self, रावणस्य Ravana's, आज्ञाप्रतीक्षा waiting for his orders, दुर्धर्षा unassailable, अहम् I, इमां नगरीम् this city, रक्षामि Iam protecting.
"In obedience to the orders of the great demon king, Ravana, I am protecting this unassailable city.