Markandeya said–‘Manu ruled over Ayodhya during Swayambhuva manvantar. One day, while he was going to sleep, he heard a peculiar sound, as if numerous small bells were ringing. He was perplexed and could not ascertain the cause of that sound so he asked sage Vashishtha about this. Sage Vashishtha made a revelation by which Manu was startled. Sage Vashishtha told him–
‘There is a holy place called Tripuri situated at the bank of river Narmada. The sound that you heard last night emanated from the small bells attached to number of aircraft kept on the roofs of the residences of such people who are virtuous. O king! Only Narmada is capable of giving salvation to lowly of sinners.’
Manu was highly impressed and decided to go to Tripuri along with his whole clan. All of them took holy dips in the Narmada and became liberated from all their sins. Manu performed a grand yagya at the bank of Narmada to which all the sages and hermits were invited. Narmada became pleased by his devotion and expressed her willingness to fulfill any wish that Manu desired.
Manu requested her help in bringing down Ganga and other holy rivers to earth. Narmada blessed him and said– ‘In the first half of Treta yuga, one of your descendants named Bhagirath would accomplish this great feat of bringing down holy Ganga to earth. In the second half of the same era other holy rivers like Kalindi, Saraswati, Sarayu, and Mahabhaga would also manifest themselves. ‘