In which book vrata of Thrusday is mentioned ? Could anyone share details of this vrata?

Question

In which book vrata of Thursday is being mentioned. Is this vrata done for God Vishnu ? I want details about this vrata . How is it to be done ?

Answer 1

There doesn't seem to be a any mentioned scriptural connection between a Thursday fast and god Vishnu.

Agni Purana, for instance just mention that a Thursday fast, protects from planetary afflictions, much like a Wednesday fast, or a Saturday fast, as mentioned in the same chapter:

Chapter 195 - Vows relating to the week-days (vāra-vrata)

अनुराधे देवगुरुं सप्तनक्ती ग्रहार्तिनुत् ॥ १९५.००५ ॥

5. One who eats only in the night on Thursday in (the asterism) anurādhā seven times would destroy all afflictions due to planets.

Garuda Purana however, says Vishnu should be worshipped on all days of the week, month, year.

Chapter CXVI - Enumeration of the names of Vratas (vows and penances) commenced

व्रतानि व्यास वक्ष्यामि हरिर्यैः सर्वदो भवेत् । सर्वमासर्क्षतिथिषु वारेषु हरिरर्चितः ॥ १,११६.१ ॥
एकभक्तेन नक्तेन उपवासफलादिना । ददाति धनधान्यादि पुत्रराज्यजयादिकम् ॥ १,११६.२ ॥

O Vyasa, by which a mart may win the good graces of the god Hari to the extent that he may be pleased to answer all his prayers. The god should be worshipped in all months of the year and in all days of the week, and under the auspicîes of all lunar phases and astral combinations. The votary shall observe a fast or take a single meal in the night, or live upon a fruit regimen on the day of the vow, and make gifts of money and paddy for the satisfaction of the god Vishnu, for which he will be blest with the birth of a son and the ownership of fresh landed estates.

---

Further, from perspective of jyotiṣa śāstra -

Which deity to worship for a particular planet is determined by the ruling deity (Adhi Devata) and governing deity (pratyadhi devata) of the planet.

For Jupiter (Guru) - the Adhi Devata (अधि-देवता) is god Brahmâ, and Pratyadhi Devta (प्रत्यधि देवता) is Lord Indra. Read more: Here

Personally, I have seen the jyotiṣí (astrologers) recommending worship of Vishnu or Shiva, to overcome an unfavorable Jupiter (Guru).

---

To Conclude -

There doesn't seem to be any scriptural prescribed connection between doing a fast on Thursday in reference to Vishnu. The only astrological connection I know of is as per Brihat Parashara Hora śāstra, Chapter 2: Verse 5 - 7, which speak of correlation between the Vâmana avatâra and Jupiter (guru). Further, in Bhagvad Gitâ 10.24 Krishna himself identifies as Bṛhaspati amongst all priest (guru), so that connection is also significant.

Overall, perhaps this vrata connection between Vishnu, Guru and Thursday, is something similar to the popular belief of fasting for Hanumâna on Saturday to counter malefic Saturn, which however, doesn't find any scriptural basis in any Astrology treatise , as I discus in this QnA