The story of Sukanya and Sage Chyavana is mentioned in the Devi Bhagavad Purana. Legend has it that King Sharyati, his queens and only daughter Sukanaya once went on a hunting expedition. They put their tent near a pond in the forest. Nearby there was a big anthill. Sukanya saw two shining points in ant hill. Out of curiosity, she took a stick and drove them inside the shining spots.
The Ashwinikumars were pleased with fidelity and devotion of Sukanya and as a reward they made Sage Chyavana handsome and young with divine medicines.
Suddenly blood started to ooze from the two spots. The soldiers opened up the anthill and found Sage Chyavana who was meditating. The two shining spots were the eyes of the Sage.
Sage Chyavana had been meditating for several years and his entire body was covered up by anthill.
Blinded and unbearable pain made Sage Chyavana angry and he was about to curse the princess, when her father intervened and asked for pardon.
Sage agreed to not to curse, if the king agreed to marry his daughter to him. The sage argued that a blind man constantly needs to help of loyal and devoted person.
Princess Sukanya, who realized her mistake, agreed to marry old Chyavana.
Years passed and Chyavana was happy with his devoted and beautiful wife.
Once Ashwinikumars, the divine physicians, happened to see Sukanya and took pity on her. They asked her to abandon the old ugly sage and marry a young man. Sukanya condemned them and chastised them that if they said anything unwanted about her husband then she would curse them.