Second Book of Esdras (Author Nehemias or Esdras or both)
8:18legit autem in libro legis Dei per dies singulos a die primo usque ad diem novissimum et fecerunt sollemnitatem septem diebus et in die octavo collectum iuxta ritum
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.