Jñānavāpī means the Well of Knowledge. It is a sacred tīrtha within Kāśī, near the self-manifested Liṅga of Viśveśvara. Īśāna dug it with his trident in the Satya Yuga so that he could bathe that Liṅga. The Kāśī Khaṇḍa gives two chapters to its origin and to the account of the brāhmaṇa girl Suśīlā, who worshipped here. The tīrtha is linked with Daṇḍapāṇi.

Origin: Īśāna digs the well

In the Satya Yuga, before clouds had rained and before rivers had flowed, Īśāna came wandering through the early universe. Īśāna is the north-eastern form of Rudra. He reached Ānandakānana, the sacred forest of bliss, which is Kāśī.

There he saw the self-manifested Liṅga of Viśveśvara. This is the Liṅga that arose at the dawn of creation, in the dispute between Vishṇu and Brahmā. Many devas, ṛshis, Siddhas, Gandharvas and Vidyādharī women were worshipping it. It was adorned three times a day, and divine women fanned it with cāmaras.

Devotion moved Īśāna. He decided to bathe the Liṅga with potfuls of cool water. He found no well or river, so he dug a deep pit to the south of Viśveśa with his blazing trident.

Columns of water rose from the pit and flooded the whole world. The water sparkled like pure consciousness. It was cool as nectar and smelled of lotus and pāṭalā flowers. It was sweeter than ambrosia and purer than pañcāmṛta. With it Īśāna bathed the great Liṅga a thousand times, using pitchers with a thousand streams. (Kāśī Khaṇḍa, Chapter 33)

How it got its name

Bhagavān Viśveśvara was very pleased with this act of devotion. He said to Īśāna: “I am pleased beyond measure. Ask for a vara (a boon). There is nothing that cannot be given to you today.”

Īśāna’s wish was simple. He asked that this unequalled tīrtha be named after Bhagavān Viśveśvara. Viśveśvara said: “The learned say that ‘Śiva’ means jñāna, knowledge. Here, by my greatness, that knowledge has become liquid. It has taken the form of water. So this tīrtha will be known in all three worlds as Jñānoda.” (Kāśī Khaṇḍa, Chapter 33)

The tīrtha has these other names:

Jñānavāpī, the well of wisdom
Śiva Tīrtha, Śiva’s own tīrtha
Tāraka Tīrtha, the tīrtha of liberation
Moksha Tīrtha, the tīrtha of salvation
Jñānoda, the flood of knowledge

Only remembering the name Jñānoda makes pāpa (sin) perish. Seeing the water, touching it, bathing in it and drinking it all bring puṇya (merit). Goblins, ghosts, evil planets, epilepsy and all kinds of affliction die down at the sight of the waters of Jñānavāpī. (Kāśī Khaṇḍa, Chapter 33)

Rewards of Jñānavāpī

The Kāśī Khaṇḍa names these rewards (phala):

Touching the water gives the puṇya of an Aśvamedha. Touching it and rinsing the mouth gives the puṇya of both the Rājasūya and the Aśvamedha.
Śrāddha offered here equals śrāddha at the Phalgu tīrtha at Gayā. On special conjunctions it gives ten million times more than Gayā.
Offering piṇḍa here every day equals offering at Kurukshetra at a solar eclipse.
Bathing the Liṅga with Jñānavāpī water equals bathing it with the water of all tīrthas.
The morning sandhyā done here at once destroys all the pāpa of neglected duties.
Sons who offer piṇḍanirvāpaṇa here rejoice in Śivaloka for a whole kalpa.
A devotee who fasts on the eighth and fourteenth lunar days and drinks this water three times has three Liṅgas fill the heart. This is the inner sign of deep Śiva-bhakti.

(Kāśī Khaṇḍa, Chapter 33)

Suśīlā and Kālavatī

The Kāśī Khaṇḍa tells of the brāhmaṇa girl Suśīlā to show the power of this tīrtha across births. She worshipped Jñānavāpī in Kāśī every day.

Suśīlā was a girl of unmatched beauty and perfect character. She was the daughter of a brāhmaṇa named Harisvāmi. She worshipped Jñānoda daily with such intensity that she began to see the whole universe filled with Liṅgas. Because she lived so close to the tīrtha, three Liṅgas arose inside her own body.

One night she was asleep in her father’s courtyard. A Vidyādhara youth carried her off through the air. An asura named Vidyunmāli met them in mid-air and fought the Vidyādhara. Both fell mortally wounded. The asura gained a divine body because of the three Liṅgas inside the girl. The Vidyādhara died remembering her with his last breath. Suśīlā was struck with grief at his death and gave her body to the fire of separation.

In the next birth the Vidyādhara was born as Mālyaketu, son of King Malayaketu. Suśīlā was born as Kālavatī in Karṇāṭa. In time they married.

Kālavatī carried the impression (saṃskāra) of her devotion in her last life. Of her own accord she liked Rudrāksha beads better than jewels and vibhūti (sacred ash) better than sandalwood paste. Her husband showed her a painting of Kāśī. She knew all the tīrthas of her past birth in it: Lolārka, Varaṇā and Maṇikarṇikā. She thrilled with recognition, for she knew them to be her eternal home. (Kāśī Khaṇḍa, Chapter 33)

Jñānavāpī and Daṇḍapāṇi

The Kāśī Khaṇḍa says that after the rites at Jñānoda Tīrtha, the devotee must please Daṇḍapāṇi, the supreme Yaksha protector of Kāśī, to finish the duty fully. Bhagavān Śiva says in the same place: “Only he who, after performing libations in the Jñānoda Tīrtha, pleases Daṇḍapāṇi, the chief of the Gaṇas, will be fully satisfied, as one who has done his duty.” So the two are bound together in the pilgrimage of Kāśī. (Kāśī Khaṇḍa, Chapter 32)

Sources

Skanda Mahā Purāṇa, Kāśī Khaṇḍa, Chapters 33–34
Skanda Mahā Purāṇa, Kāśī Khaṇḍa, Chapter 32 (Daṇḍapāṇi)