SB 9.7.20
sastham samvatsaram tatra
caritva rohitah purim
upavrajann ajigartad
akrinan madhyamam sutam
sunahsepham pasum pitre
pradaya samavandata
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Thereafter, in the sixth year, after wandering in the forest, Rohita returned to the capital of his father. He purchased from Ajigarta his second son, named Sunahsepha. Then he offered Sunahsepha to his father, Hariscandra, to be used as the sacrificial animal and offered Hariscandra his respectful obeisances.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It appears that in those days a man could be purchased for any purpose. Hariscandra was in need of a person to sacrifice as the animal in a yajña and thus fulfill his promise to Varuna, and a man was purchased from another man for this purpose. Millions of years ago, animal sacrifice and slave trade both existed. Indeed, they have existed since time immemorial.