(Brhaspativar) Jupiter is the ruling planet of the fifth day
of the week (Brhaspati).
Because the sage Brhaspati is the religious preceptor (guru)
of the gods in Hindu mythology, another common name for Thursday is Guruvar.
Jupiter is an extremely powerful planet in Hindu astrology
(jyotisha), and because one's spiritual preceptor is often likened to a god in
religious life, this makes Thursday a ritually important and powerful day.
On this day, one's religious preceptor is one of the
"deities" to be honored and served.
On this day, the goddess Lakshmi, who is mostly venerated by
women, is also honored.
Lakshmi is the goddess Vishnu's wife and the personification
of riches, happiness, and good fortune, which she carries with her everywhere
she goes and takes away when she departs.
Married women worship her as the human equivalent of Lakshmi
in order to achieve these things or to keep them if they already have them.
Because it is commonly known that good fortune is fleeting
and may change at any time, Lakshmi is also seen as a capricious and fickle
celestial presence.
Changing jewelry on that day is one of the taboos for women,
at least in areas of northern India, since it is supposed to agitate Lakshmi
and heighten the risk of her departing due to her annoyance.
A tiger or lion is the animal vehicle of the Goddess's
strong incarnations, such as Durga, in Hindu mythology.
The fact that the Hindi term sher may refer to any animal is
reflected in modern iconography, which depicts both lions and tigers with no
discernible differences.
In any instance, the Goddess riding such a hazardous animal
is definitely a representation of her strength and capability, since these
creatures are often represented as her friends in her mythology, fighting on
her behalf in answer to her commands.