Srimad Bhagvata Mahapurana: Book 9: Chapter 7: Verses 1-15
The story of the King Hariscandra
Sri Suka resumed : The foremost of the (three) sons (Purukutsa and others) of Mandhata, who was celebrated by the name of Ambarisa, was adopted (as a son) by his grandfather (Yuvanaswa) and Yauvanaswa was the son of Ambarisa. Narita was the son of Yauvanaswa. These (three) turned out to be the foremost of Mandhata's line (and the first of three branches of this line). Purukutsa (the eldest of the three* sons of Mandhata) was taken to Rasatala (the sixth of the subterranean spheres from above) by Narmada, as directed by Vasuki (the king of serpents)-the same Narmada who had been given to him in marriage by his brothers, the serpent-demons. There indeed Purukutsa (who wielded the power infused into him by Lord Visnu) killed (a number of) Gandharvas who (being enemies of the Nagas and wicked too) deserved to be slain. (In recognition of this service) he secured from Vasuki (the chief of the Nagas) the boon of security from the serpent race for those who remember this anecdote. Purukutsa's son (named after his grandfather was Trasaddasyu, who was the father of Anaranya. Anaranya's son was Haryaswa and of Haryaswa, Aruna was born; while from (the loins of) the latter sprang up Tribandhana. Tribandhana's son, Satyavrata, became celebrated under the name of Trisanku. Having got the rank of a Candala (pariah) under a curse from his father, he bodily ascended to heaven by virtue of the extraordinary might of the sage Viswamitra (a scion of Kusika) and can be seen in the heavens (in the form of a star of that name) even to this day, having been forcibly stopped (in mind air) by the same seer when hurled, head downward, by the gods (from heaven).
Trisanku's son was Hariscandra, because of whom there raged a fight, lasting for many years, between the sages Viawamitra and Vasistha, who (having been mutually cursed) had been transformed into two birds*. Devoid of (any) issue and (therefore) sad at heart, Hariscandra sought, under the instructions of (the sage) Narada, Varuna (the god of water) as his protector with the following prayer:-"Let a son be born to me, 0 lord ! If he turns out to be a hero, O great lord, I shall propitiate you by sacrificing him (to you)." Varuna granted his prayer, saying "Be it so ! and through the agency of Varuna a son, Rohita (by name), was born to Hariscandra. "Now that a son has been born (to you), propitiate me, dear king, by sacrificing him to me," Varuna (appeared and) said (to Hariscandra, who replied): "A prospective victim is (considered) fit for being sacrificed only when it has passed the age of ten days." On the child having crossed (the limit of) ten days, the god appeared (before him again) and said, "(Please) sacrifice the child now." Hariscandra (however) replied, "A prospective victim is (deemed) fit for being sacrificed only when it has teethed." After the dentition of the child, Varuna (approached and) said once more, "The teeth have (already) appeared; (please) propitiate me (now)." Thereupon the king replied, "When its (first) teeth have fallen, the victim will be fit for being sacrificed (only) then." (On the teeth having fallen) Varuna (appeared once more and) said, "The teeth of the prospective victim have (already) fallen, (please) worship me (now)." (To this) Hariscandra replied, "When the teeth of the prospective victim sprout again, then (alone) is the prospective victim (regarded as)
 sacred." (On the child having teethed again) the god of water (appeared and) said once more, "The teeth have grown again, (please) sacrifice the child (now)." Thereupon Hariscandra replied, "A prospective victim belonging to the Ksatriya race is (recognized as) sacred (fit to be sacrificed) only when he is able to put on his armour, 0 lord I" In this way the god (of water) waited for the time he was asked to wait by Hariscandra, whose mind was bound with ties of affection and who was gaining time due to love for his son.