Second Book of Paralipomenon (Author Compiled by Isaias and Esdras from records of Nathan, Gad, Addo, Ahias, Jehu and others.)
2:18fecitque ex eis septuaginta milia qui umeris onera portarent et octoginta milia qui lapides in montibus caederent tria milia autem et sescentos praepositos operum populi
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.