Mahabharata 12.326.78

12.326.78

saṃdhau tu samanuprāpte tretāyāṃ dvāparasya ca |
rāmo dāśarathirbhūtvā bhaviṣyāmi jagatpatiḥ || 78 ||

When after routing the Lord of Sachi, that Asura will take unto himself the sovereignty of the three worlds, I shall take birth in Aditi's womb, by Kasyapa, as the twelfth Aditya. I shall (taking the sovereignty of the three worlds Vali) restore it to Indra of immeasurable splendour, and replace the deities, O Narada, in their respective stations. As regards Vali, that foremost of Danavas, who is to be unslayable by all the deities, I shall cause him to dwell in the nether regions. In the Treta age I shall take birth as Rama in the race of Bhrigu, and exterminate the Kshatriyas who will become proud of their strength and possessions. Towards the close of Treta and the beginning of Dwapara, I shall take birth as Rama, the son of Dasaratha in Iskshaku's royal line. At that time, the two Rishis viz., the two sons of Prajapati, called by the names of Ekata and Dwita, will in consequence of the injury done by them unto their brother Trita, have to take birth as apes, losing the beauty of the human form. Those apes that shall take birth in the race of Ekata and Dwita, shall become endued with great strength and mighty energy and will equal Sakra himself in prowess. All those apes, O regenerate one, will become my allies for accomplishing the business of the deities. I shall then slay the terrible lord of the Rakshasas, that wretch of Pulastya's race, viz., the fierce Ravana, that throne of all the worlds, together with all his children and followers.