According to old hindu mythology, once Narad ji went to Mata Parvati and started to praying virtuous religious of Goddess Anusuya. The three ladies present there got jealous of this.After the departure of Narad ji , those three ladies started started discussing about breaking piety religion of Goddess Anusuya, wife of Atri rishi
Asa a result , all three goddesses asked their husbands to break the virtuous religion of Goddess Anusuya.
Being compelled tridev (Brahma + Vishnu + Shiva )reached the ashram of Goddess Anusuya in the form of beggars. Goddess Anusuya brought alms, but tridev refused and desire to have food . Goddess Anusuya agreed , prepared food and call them to eat . Tridev sat down on seat and asked Goddess Anusuya to serve food naked.
Godess Anusuya was angry at first , but later recognized Tridev(Brahma , Vishnu Mahesh) through her tabobal. Then made tridev in form of child and then she fed all food and made all them sleep.
Tridev did not return . Then all three wives of tridev started worrying and went to Godess Anusuya and asked for forgivenesss for their mistake.
The three goddesses asked Tridev to be returned . Devi Anusuya refused . Then the three Goddesses created Dattatreya from the part of Brahma , Vishnu and Shiva and handed them over to Godesss Anusuya as a son . Having found Dattatreya in the form of a son , Goddess Anusuya , with her tapobal made tridev in his origanal form . Thus Lord Dattatreya was born.