Valmiki Ramayana Yuddha Kanda Sarga 116 Shloka 12
Original Shlokaसम्भ्रमश्च न कर्तव्योवर्तन्त्यारावणालये ।।6.116.12।। विभीषणविधेयंहिलङ्कैश्वर्यमिदंकृतम् ।
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रावणालये Ravana's abode, वर्तन्त्या staying, सम्भ्रमः च perturbation, न कर्तव्यः not required, इदम् this, लङ्कैश्वर्यम् Lanka's Lord, विभीषणविधेयम् under Vibheeshana, कृतंहि has become
"This Lanka is under Vibheeshana, Lord of Lanka. There is no need for perturbation thinking that you are in Ravana's abode."