Tamasa River is mentioned in several Puranas in Hinduism. Today, the river is known as Tons and flows through Azamgarh in Uttar Pradesh and joins Ganga near Ballia.
Legend has it that the ashram or hermitage of Sage Valmiki was located on the banks of Tamasa River. Therefore, the epic Ramayana was composed on the banks of the river.
It was on the bank of Tamasa River Bhagavan Sri Ram, Mata Sita and Lakshman made their first halt after Rama was banished from Ayodhya and exiled for 14 years.
As per Uttara Ramayana, Mata Sita, when exiled by Sri Ram, also lived on the banks of Tamasa River. She delivered her two sons, Lava and Kusha, here.