Valmiki Ramayana Ayodhya Kanda Sarga 33 Shloka 22

राघवः scion of the Raghus, येन wherever, गच्छति is going, वनमेव forest itself, नगरम् as city, अस्तु shall be, अस्माभिः by us, परित्यक्तम् deserted, पुरं च the city also, वनम् as forest, सम्पद्यताम् may become.

Since the scion of the Raghu race is going to the forest, let that forest itself be our city and let the city deserted by us become the forest.