Ramayana
वरदानकृतत्राणे सा गदा रावणोरसि । दुर्बलेव यथावेगं द्विधाभूत्वा ऽपतत्क्षितौ ॥ 7-32-61 ॥
But upon Ravana's chest, protected by the boon he had been granted, that mace, as though feeble, broke in two with all its force and fell to the ground.
english translation