Valmiki Ramayana Ayodhya Kanda Sarga 61 Shloka 11

राघवः Rama, पञ्चदशे वर्षे in the fifteenth year, पुनः एष्यति यदि if returns, भरतः Bharata, राज्यं च kingdom, कोषं च treasury too, जह्यात् will give up, नोपलक्ष्यते it does not appear.

Even if Rama returns in the fifteenth year, it is unlikely that Bharata will give up the kingdom and royal treasury (in favour of Rama).