The following story narrates the history of how Datta Guru was born and started his mission on Earth.
Anasuya the wife of Sage Atri was very chaste (pativrata). Her chastity endowed her with so much power that Indra and other deities felt threatened. They approached Brahma, Vishnu and Mahesh and beseeched Them to test Her chastity.
Once when Sage Atri had gone out to undertake austerities the trinity of deities disguised as guests approached Anasuya and asked for alms. She requested Them to wait till Sage Atri returned. They replied saying, “It will be long before the sage returns. We are very hungry. Please serve us fast otherwise we will go elsewhere. We have heard that you serve guests food as per their wishes in your hermitage, that is why we had come.” Then she welcomed Them and requested Them to sit down for a meal. They complied. When she came to serve Them They said, “Seeing your beauty we wish that you serve us without any garments on.” She thought to herself, “It is wrong to send a hungry guest away. My mind is pure, then what can Kamadev do? The prowess of my husband’s penance will save me.” She then told the guests “I will serve You so. Eat to Your heart’s content.” In the kitchen she meditated upon her husband and thought ‘these guests are my children’. Then she removed her garments and came to serve Them. To her surprise, the guests had turned into three wailing babies ! She then nurse Them and thus stoppedTheir cry.
Just then, Sage Atri returned. She narrated everything to Him. He being Omniscient recognised the babies and offered obeisance to Them. The babies remained in the cradle and Brahma, Vishnu and Mahesh appeared before the couple. Appeased, the deities told the couple to ask for a boon. Atri and Anasuya asked for the babies to remain with them. Blessing them accordingly, the deities returned to Their abodes. From the three deities, Chandra was created from Brahma, Datta from Vishnu and Durvas from Shankar. Chandra and Durvas took permission and left for the chandra region (chandralok) and to places of pilgrimage respectively, to undertake penance. The third, that is Datta remained on the earth to accomplish the mission of Deity Vishnu. This itself is the origin of the Guru lineage (pitha).