It falls right One day before Radha Ashtami festival, hence it is also called Lalita Saptami, Goddess Lalita is one of the eight prominent companions of Radha Ji. This day has been dedicated to him due to being the most beloved friend of Shri Radharani and Lord Krishna. It is a very auspicious day and holds a great significance.
On fasting, at devotee should worship Shiva-Parvati again in the afternoon with sandalwood, akshat, incense, lamp, naivedh, betel nut and coconut etc. During Saptami Tithi fast, prashad of kheer-puri and sweets (Gudd Ke Puee) is made as naivedya. To protect the child, Lord Bholenath is offered Kalava and after wearing it himself, one should listen to the story of this fast.
The story of Santan Saptami Fast :-
Once Shri Krishna told Yudhishthira that sometime Lomash Rishi came to Mathura. My parents Devaki and Vasudev served them devoutly, then the sage ordered them to recover from the mourning of the sons killed by Kansa - "O Devaki! Kansa has mourned your son after killing many of your sons. To get rid of this sorrow, you observe 'Santan Saptami'.
King Nahusha's queen Chandramukhi also did this fast. Then even her sons did not die. This fast will also free you from mourning son. Then Devaki asked- "Hey, God! Please tell me the complete method of fasting, so that I can perform the fast in a systematic way. Lomash Rishi also told him the fast story by telling him the worship of the fast.
Friendship of Chandramukhi and Roopwati :
Nahush was the majestic king of Ayodhya. His wife's name was Chandramukhi. A Brahmin named Vishnudatta lived in his kingdom. His wife's name was Roopvati. Rani Chandramukhi and Roopwati had a close friendship. One day both of them went to bathe in Saryu river. Other women were also taking bath there.
Those women made a statue of Parvati and Shiva there and worshiped them methodically. Then Queen Chandramukhi and Roopvati asked the women the name and method of worship. One of those women told- "We have worshiped Shiva along with Parvati. By tying the thread of Lord Shiva, we have comitted for that this vow and we will continue as long as we live. This 'Muktabharan Vrat' brings happiness and children.
Vow the Resolution :
After listening about that fast, both of those friends also commited to observe this fast throughout their life and tied a thread in the name of Shiva. But after reaching home, they forgot the resolution. As a result, after death the queen born as a monkry and Brahman Lady were born as a chicken. Later, both after the animals life born back as the human.
Chandramukhi became the queen of King Prithvinath of Mathura and Rupwati again took birth in a Brahmin's house. In this birth, the name of the queen was Ishwari and the name of the Brahmin was Bhushana. Bhushana was married to Rajpurohit Agnimukhi. Even in this birth, both of them became friends.
Due to forgetting the fast, the queen was deprived of happiness of a child even in this birth. She gives birth to a dumb and deaf son in old age, but he also died at the age of nine years. Bhushana remembered the fast. So eight beautiful and healthy sons were born from her womb.
One day Bhushana went to meet Queen Ishwari's son for condolences. After seeing her, there was envy in the mind of the queen. She sent Bhushana, And invite to hes sons for food and added poison to the food. But due to the effect of fasting of Bhushana, even a hair of her children was not deterred.
This enraged the queen even more. She ordered his servants to take the sons of Bhusna to the banks of the Yamuna on the pretext of worship pushed them into deep water. But this time also the children of Bhushana survived by the effects of fasting due to the grace of Lord Shiva and Mother Parvati.
As a result, the queen summoned the executioners and ordered that the Brahmins boys will be killed by taking them to the slaughter site, but even after the best efforts by the executioners, the children could not die. The queen was surprised to hear this news. He called Bhushana and told him the whole thing and then apologized and asked him - "Why did your children not die?"
Bhushana said- "Don't you remember the previous birth? The queen said with surprise-" No, I don't remember anything? "Then Bhushana said-" Listen, you were the queen of King Nahusha in the previous birth and I was your friend.
Both of us had once tied the thread of Lord Shiva and commit that for our child we will observe 'Santan Saptami' fast. But unfortunately we forgot and due to the disregard of the fast, taking birth in different births, now as humans we have born again. Now I remembered that fast, so I peformed. Due to the effect of this, you could not get my sons to die either.
"On hearing this, Queen Ishwari also methodically kept this 'Muktabharan Fast' for a child. Then the queen got pregnant again and gave birth to a beautiful child. This fast is practiced for the attainment of son from time and to protect the child by the Indian women.
