This fast is usually undertaken by married women, but even unmarried girls observe it these days, usually on Amaveseya (dark night) in order to avoid widowhood and remain as wife till the husband lives. Banyan (Vata) tree is worshipped on this day. The prayer, "May I abide in heaven as many years, as this tree continues growing on the earth." Ashvapati, the king of Bhadra region, and his wife, after undertaking fasts and invoking Goddess Savitri (Saraswati) were blessed with a baby girl, a personification of the Goddess herself, bearing the name Savitri. On attaining adulthood, Savitri was allowed by the parents to go round and find a suitable match for herself. On return from this long trip, Savitri informed her parents that she had selected Sateyvan, the son of exiled and blind father Dhumatsen.
Narada, the teacher among gods (Devrishi), who was present on the occasion, made some astrological calculations, congratulated Ashvapati, appreciated the attributes of Sateyvan, but also prophesied that after one year of the marriage of Savitri, Sateyvan would die. Dismayed, the parents desired Savitri to select some other person, but Savitri refused saying that the husband is made once and for ever. At last the marriage was performed. Savitri started enjoying her life in the forest, cutting and collecting fuel day by day, cut by her husband. Savitri accompanied her husband every day and never stayed back.
Four days before the completion of one year of their married life, Savitri undertook fast for three days and kept sitting still by day and night. On the fourth inauspicious day, she got up early, finished her daily routine, recited her prayer, paid respects to her in laws. Meanwhile Sateyvan came out with his axe and was ready to go to the forest, to bring fuel wood, as per his daily routine. Savitri was also ready to go with him, but he discouraged her from going, but she did not agree and with permission of her in laws, went with Sateyvan. When at work, Sateyvan felt a little giddy, came down the tree and lay on the ground. Savitri remembered Narada's prophecy and she made up her mind to face the consequences.
Sateyvan, then died in the lap of Savitri, Yama (God of death) came, took out the soul of Sateyvan's body and started going towards Yamlok (Yama's abode in heaven). Savitri followed Yama; on being asked to return Savitri said, "Wherever my husband goes, I shall go. This is my eternal faith, worship, devotion, love for the husband, the power of fasting and by your kindness, my step will not stop anywhere."
Yama: "0' Savitri, I am very happy to listen to your dialogue and determination. Except for the life of Sateyvan, you may ask any boon from me."
Savitri: "My in-laws are blind and have lost their kingdom. May they get their eyesight and be healthy and enlightened."
Yama: "Be it so". The Yama advised Savitri to go back and avoid exertion.
Savitri: "How can there be exertion without the husband? I shall find shelter where my husband goes; so take me there. Company of a noble man, even for little while, is benignant. It is still more important if one falls in love with such a one. Austerities never fail, so one should always be with noble persons."
Yama: "Savitri, I appreciate your talk on welfare, which will also add to the wisdom of the intellectuals. Therefore, except for Sateyvan's life, ask any other boon."
Savitri: "My father-in-law has lost his kingdom; May he regain it and be a righteous ruler."
Yama: "Be it so; now you go back."
Savitri: "You control this whole universe and by arrangement, give them their cherished success, so you are called Yama, the Dharmaraja. Truly veracious people have a religious duty to be kind to all with their thoughts, speech and action. Veritable persons are ever kind on their enemies, as against ordinary persons."
Yama: "0' benedictory, your speech is like water to a thirsty one. I am happy; so except for Sateyvan's life, ask any other boon."
Savitri: "My father king Ashvapati has no son. I ask your boon that he should have a hundred valiant sons, to continue his progeny."
Yama: "Be it so. Now your desires have been fulfilled, so return."
Savitri: "Because I am going with my husband, so this distance is not much for me. You are the son of Surya (Sun), so you are called Veyvasvat. You treat the friends and enemies alike, so you are called Dharmaraja (King of justice). The men like veritable saints and have faith in them." Yama: "0' beautiful, your saying is true and I have never heard such before; so except for Sateyvan's life, ask any other boon."
Savitri: "My fourth desire is that I should have a hundred powerful and valiant sons, like Sateyvan." Yama: "0' young one, you will have a hundred sons, by virtue of them, you will be very happy."
Savitri: "Right persons always cling to their religion; they are never unhappy. Right persons, in company with right ones, always profit. Saints are never afraid of other saints. They are the past and the future. This ancient religion Dharma is served by righteous saints. They do good to others and never look back."
Yama: "The more you talk to me about serious now you ask some matchless boon."
Savitri: "Oh great lord; the boon of hundred sons awarded by you cannot be fulfilled without a husband. Now, I ask you this boon that Sateyvan be restored to life. Thereby your boon of my hundred sons will also be fulfilled. So I demand life for Sateyvan, so that your promise should not become a lie".
Yama was immensely pleased and said, "Be it so." Yama came back to earth with Savitri, put the soul back into Sateyvan's body and disappeared. Sateyvan got up and all were happy to return to their parents and their kingdom.
The legend proves the power behind "Savitri Fast", undertaken inreverence to Savitri (Saraswati) goddess by women, to ensure long life for their husbands.