Henry Chadwick (1993). The Early Church(en inglés). Penguin. ISBN978-1-101-16042-8. «Hippolytus in the Apostolic Tradition directed that Christians should pray seven times a day - on rising, at the lighting of the evening lamp, at bedtime, at midnight, and also, if at home, at the third, sixth and ninth hours of the day, being hours associated with Christ's Passion. Prayers at the third, sixth, and ninth hours are similarly mentioned by Tertullian, Cyprian, Clement of Alexandria and Origen, and must have been very widely practised. These prayers were commonly associated with private Bible reading in the family.»
