Ramayana
नह्ययं रावणो युद्धे शक्यो जेतुं सुरासुरैः । न भवन्तः क्षयं नेतुमपि सामरदानवैः ॥ 7-23-12 ॥
Truly this Ravana cannot be conquered in battle by the gods and the asuras; nor can you be brought to destruction, even by the gods and the danavas together.
english translation