The Tamasā (modern Tonse) is a sacred river. It forms the southern boundary of the holy kshetra of Ayodhyā. It rises in a dense forest that was the tapas-grove of Maṇḍavya Maharshi, and the āśramas of Maṇḍavya, Gautama, Cyavana and Parāśara lie on its banks.

The Skanda Mahā Purāṇa describes the river’s beauty in rich detail. It says that a holy bath in the Tamasā on the full-moon day of Mārgaśīrsha gives great benefit. A special Sītākuṇḍa and the Śiva liṅga Dugdheśvara lie near the river inside Ayodhyā’s sacred zone.

Location and sacred boundary

The Tamasā flows south of Ayodhyā. It is the southern boundary of the sacred kshetra of Ayodhyā, just as the Sarayū is the northern boundary. These two rivers hold the holy city between them. The Skanda Mahā Purāṇa, Vaishṇava Khaṇḍa, Ayodhyā Māhātmya, says this.

Origin: the forest of Maṇḍavya

The Tamasā begins in a forest where the great ṛshi Maṇḍavya performed his tapas (austerity). The Purāṇa calls that forest holy and full of puṇya (merit), and an excellent region.

The tapas-grove is made lovely by spreading creepers, hedges and bushes in full bloom, and by a dense cover of trees. The trees named are Priyaṅgu, Ketaka, Tamāla (Indian cinnamon), Karṇikāra, Bakula, Aśoka and Punnāga. Swarms of bees hover among the flowers. Birds of every kind fill the air with their calls, among them ruddy geese, Kadamba geese and Kāraṇḍava ducks. The forest is also adorned with blue-green Nicula trees and with peacocks, with fresh sprouts and tender shoots, and it is rich in fruit. The Skanda Mahā Purāṇa, Vaishṇava Khaṇḍa, Ayodhyā Māhātmya, Chapter 9, gives this description.

Āśramas on its banks

Several great ṛshis had their āśramas on the banks of the Tamasā.

Maṇḍavya: His tapas-grove and āśrama are at the source-forest itself. Through the power of this ṛshi the Tamasā stays pure and sacred for ever.
Gautama: His great holy āśrama lies to the east of Maṇḍavya’s grove.
Cyavana: His āśrama lies further east, beyond Gautama’s.
Parāśara (the father of Vyāsa): His āśrama, called a storehouse of tapas, is also among those on the banks of the Tamasā.

The Purāṇa says there are tīrthas (pilgrimage places) of many kinds and āśramas of great ascetics all round along the Tamasā. This makes the whole bank a path of holy power.

Rites and their merit

A holy bath, gifts in charity, and śrāddha performed on the banks of the Tamasā always destroy all pāpa (sin) and give all that one desires. The special yearly bath is prescribed for the full-moon day in the bright half of the month of Mārgaśīrsha, and it gives great benefit. The Skanda Mahā Purāṇa, Ayodhyā Māhātmya, Chapter 9, says this.

Other tīrthas on the Tamasā

More tīrthas lie near the Tamasā inside Ayodhyā’s sacred zone.

Sītākuṇḍa (on the Tamasā): This is a second Sītākuṇḍa, near Dugdheśvara and separate from the first Sītākuṇḍa near Guptahari. Its yearly festival falls on the fourth day of the bright half of Bhādrapada. Bhagavān Vighneśvara is worshipped there to remove all obstacles.
Dugdheśvara: This is a Śiva liṅga that appeared in the milk flowing from the udders of Kāmadhenu when Bharata came to receive Rāma at Siddhasthāna. Vasishṭha named the liṅga, and Rāma worshipped it. People who bathe in the Sītākuṇḍa on the Tamasā and visit Dugdheśvara are freed from all pāpa.
Bhairava: He lies south of the Tamasā Sītākuṇḍa and is guarded by Vāsudeva. His yearly festival falls on the eighth day of the dark half of Mārgaśīrsha.

The Skanda Mahā Purāṇa, Ayodhyā Māhātmya, Chapter 9, gives all three.

In the Vālmīki Rāmāyaṇa: Rāma’s first night of exile

In the Ayodhyā Kāṇḍa of the Vālmīki Rāmāyaṇa, the Tamasā is the place of the first night of Rāma’s forest exile. Rāma, Sītā and Lakshmaṇa left Ayodhyā in a chariot driven by Sumantra. They travelled south until evening and halted on the bank of the Tamasā. The Ayodhyā Kāṇḍa shows the river there as lovely and calm, with clear and pleasant water.

A great number of the people of Ayodhyā had followed the chariot on foot and would not leave Rāma. They camped near the bank of the Tamasā, weeping and refusing to turn back. That night Rāma, Sītā and Lakshmaṇa slept on the riverbank.

Before dawn Rāma had Sumantra drive the chariot quietly to a ford upstream, and they crossed the Tamasā at a different place while the people slept. When the prajā (citizens) woke and found the chariot gone, Rāma had already crossed the river and was going south into Kosala. He crossed the Tamasā without a formal farewell. The Vālmīki Rāmāyaṇa, Ayodhyā Kāṇḍa, Chapters 44–46, tells this.

Sources

Skanda Mahā Purāṇa, Vaishṇava Khaṇḍa, Ayodhyā Māhātmya, Chapter 1 (the boundary of the kshetra)
Skanda Mahā Purāṇa, Vaishṇava Khaṇḍa, Ayodhyā Māhātmya, Chapter 9
Vālmīki Rāmāyaṇa, Ayodhyā Kāṇḍa, Chapters 44–46

Tamasā River