Valmiki Ramayana Aranya Kanda Sarga 51 Shloka 28
Original Shlokaन हि जातु दुराधर्षौ काकुत्स्थौ तव रावण।।3.51.28।। धर्षणं चाश्रमस्यास्य क्षमिष्येते तु राघवौ।
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रावण Ravana, दुराधर्षौ both invincible, काकुत्स्थौ both Kakutsthas, राघवौ Rama and Lakshmana, तव your, अस्य आश्रमस्य their hermitage, धर्षणम् assault, जातु surely, न क्षमिष्येते not forgive.
O Ravana know that Rama and Lakshmana, the Kakutsthas, are invincible. They will not forgive the asssault you have made on their hermitage.