Valmiki Ramayana Yuddha Kanda Sarga 19 Shloka 1
Original Shlokaराघवेणाभयेदत्तेसन्नतोरावणानुजः । विभीषणोमहाप्राज्ञोभूमिंसमवलोकयन् ।।6.19.1।।
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राघवेण: by Raghava, अभये: promised security, दत्ते: given, रावाणानुजः to Ravana's brother, महाप्राज्ञः wise, विभीषणः Vibheeshana, सन्नतः prepared to, भूमिम् ground, समवलोकयन् looked around.
When wise Vibheeshana, the brother of Ravana was assured of security by Raghava, he looked around the ground and prepared (to descend). Descending from the sky Vibheeshana seeks refuge with Sri Rama. On enquiry Vibheeshana tells everything about Ravana to Sri Rama.