While narrating the story of Brihaspati Trayodashi Pradosha Vrat before Shaunaka and the other eighty-eight thousand sages, Suta Ji said - "Once, a fierce battle took place between Devaraja Indra and a demon named Vritra. During that battle, the Devas defeated the army of the demons through their valor. Seeing a vast number of his soldiers slain, Vritrasura became enraged and himself prepared for battle. By the power of his demonic Maya, he assumed an extremely terrifying and dreadful form and began challenging the Devas to fight.
As soon as Indra and the other Devas beheld the fearsome form of Vritrasura upon the battlefield, they became terrified and invoked Devaguru Brihaspati for assistance. Hearing the prayers of the Devas, Devaguru Brihaspati appeared there and asked them the reason for their anxiety.
Indra and the other Devas said - 'O Gurudeva! A dreadful demon named Vritra has attacked Devaloka. He is extremely powerful. Kindly help us and show us the means to overcome this crisis.'
Devaguru Brihaspati said - 'O Devendra! This Vritrasura is extremely deceitful and powerful in Maya. I will narrate his story to you, listen attentively - Vritrasura was highly ascetic and devoted. By performing severe penance upon Mount Gandhamadana, he had pleased Lord Shiva. In his previous birth, that demon was a king named Chitraratha. His kingdom was situated in a beautiful forest near your realm. Many sages, saints and great ascetics used to perform penance and spiritual practices in that forest. That place was considered highly suitable for attaining God.
Once, while wandering, Chitraratha reached Mount Kailasa. Upon Mount Kailasa, Lord Shiva was seated along with His Ardhangini Goddess Parvati and was addressing an assembly. After beholding the divine form of Lord Shiva and Goddess Parvati seated beside Him, Chitraratha folded his hands mockingly and said to Lord Shiva - 'O Bhagavan! We ordinary beings remain deluded by Maya and become attached to women, but nowhere in Devaloka have I seen anyone seated in an assembly together with a woman.'
Hearing these sarcastic words from Chitraratha, Lord Shiva smiled and said - 'O King! My practical outlook is different from all others. I have consumed the world-destroying poison Kalakuta itself. Even after this, you mock Me like an ignorant person.'
Goddess Parvati also became extremely enraged at Chitraratha. Casting Her glance upon him, Mata Parvati said - 'O wicked being! You have mocked My Lord, Mahadeva, who pervades the entire animate and inanimate universe, in My very presence. Therefore, you will certainly suffer the consequences of this sinful act. All the wise beings present in this assembly are knowers of the essence of all Shastras. Sanaka, Sanandana, Sanatana and Sanatkumara present here remain absorbed in devotion to Lord Shiva after destroying all ignorance. O fool! You consider yourself extremely clever, therefore you must learn a lesson so that never again in the future may you dare mock an assembly of saints and learned beings. I curse you that this very instant you shall fall from your celestial vehicle to Bhuloka and be born in a Rakshasa Yoni.'
As soon as he was cursed by Goddess Jagadamba, Chitraratha fell from his celestial vehicle to Bhuloka and was born in a Rakshasa Yoni, becoming infamous as Mahasura. A great ascetic sage named Tvashta, through the power of his penance, manifested that Asura in the form of Vritrasura.'
Brihaspati Ji further said - 'Vritrasura began worshipping Lord Shiva while observing Brahmacharya. As a result of his devotion to Lord Shiva, he attained immeasurable strength and valor. Therefore, since he is a devotee of Lord Shiva, you cannot defeat him. My advice is that if you wish to gain victory over that mighty demon, then you should devoutly observe the Brihaspati Pradosha Vrat.'"
Suta Ji says - "Following the counsel of Devaguru Brihaspati, the Devas observed the Guru Pradosha Vrat according to the complete rituals, as a result of which Vritrasura was defeated and the terrible crisis that had arisen in Devaloka was resolved. Likewise, whoever faithfully observes this supremely meritorious Vrat attains relief from all sufferings and fulfillment of cherished desires."
॥Iti Shri Brihaspati Pradosha Vrat Katha Sampurnah॥