 न हि जातु दुराधर्षौ काकुत्स्थौ तव रावण।।धर्षणं चाश्रमस्यास्य क्षमिष्येते तु राघवौ। 
 O Ravana  know that Rama and Lakshmana, the Kakutsthas, are invincible. They will not forgive the asssault you have made on their hermitage. 