Updated: Dec 9, 2022
Once there lived a chaste & pious lady named Anasuya, wife of sage Atri. Her loyalty toward her husband was so intense that Indra & there other gods were afraid of the power that chastity endowed her with. With malice in heart, they requested the trinity of Brahma, Vishnu and Shiva to test her.
The three gods this went to her ashram, while the husband was away, disguised as sages, asked her for food. While she got the food ready to be served, the sages mentioned about their vow to not accept food from a person who was clothed. This put Anasuya in a dilemma; she couldn't let the sages return hungry from her hut, but at the same time couldn't break her chastity too.
Finally she decided that her chastity was strong in enough to survive this situation and went inside the hut to disrobe. She concentrated on the feet of her husband, and thought of the sages to be her children, whom she was about to feed. When she came out, she found the three sages transformed into children, to her utter surprise! She then proceeded to breast feed them. The trinity was pleased and then transformed into their original forms. They blessed Anasuya with a boon. She asked for them to be born from her womb and that's how Dattatreya was born.
This story is one of the more popular one among several others, regarding Dattatreya's birth. While some mention it was the Tridevi who were jealous of Anasuya instead of Indra, while a few more mention that the three babies were merged together to form Dattatreya, to even that out of the three babies, two (Chandrama and Durvasa born from Brahma and Shiva respectively leave) leave and the one left behind is Dattatreya (from Vishnu), who has the quality of all the three gods.