The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
15. Moreover there are seven (hells).
Moreover, the purâna-writers record that there are seven hells, Raurava, &c., by name, which serve as abodes of enjoyment of the fruits of evil deeds. As those who do not sacrifice, &c. go there, how should they reach the moon?--But, an objection is raised, the assertion that evil doers suffer punishments allotted by Yama is contradicted by the circumstance that Smriti mentions different other beings, such as Kitragupta, &c., who act as superintendents in Raurava and the other hells.--This objection the next Sûtra refutes.