Jungmann, Josef A., S.J. "Chapter Nine: Daily Devotions of the Early Christians." The Early Liturgy to the Time of Gregory the Great. (translated by Francis A. Brunner, C.S.S. R., Notre Dame, Indiana: University of Notre Dame Press, 1959, pp. 97-108.
Though there are voices which suggest the entirety of early Christian life revolved around the corporate celebration of liturgy, Jungmann considers them to be incorrect (Jungmann 1959, 97). The Gospels are clear that we should expect to be involved in a life of private prayer. Jesus particularly taught his disciples both about assembling and praying privately. Further, Jungmann considers that mass gatherings may have been dangerous (Jungmann 1959, 98). The earliest of the patristic writings also prescribe prayers, typically three times a day, a custom Jungmann sees as individual prayer times which eventually grew into the liturgical hours. The observances at the third, sixth, and ninth hours of the day are clearly shown in Scripture as times when individuals would engage in prayer (Jungmann 1959, 99). Tertullian adds mention of prayers upon awakening and at bed time, as if they were so common as to have been taken for granted. He also considers a prayer in the middle of the night to have been customary (Jungmann 1959, 100). Early commentators make some mention of the customs and even the content of some of the prayers. However, Jungmann does not consider the comments very prescriptive or detailed (Jungmann 1959, 102). A seventh time of prayer may also have emerged, at the cock's crow, not the regular time to arise (Jungmann 1959, 103). The themes of the various times of prayer become associated with the hours. Jungmann sees numerous medieval sources which do just that (Jungmann 1959, 104). The growth of monasticism finished the task of making the liturgical hours a matter of corporate prayer (Jungmann 1959, 106).
Jungmann further suggests that Constantine's edict of toleration led to a greater freedom for Christians to assemble for corporate prayer. This may have moved Christians to gather at different times in the day at a central location (Jungmann 1959, 106). Hippolytus does speak of regular gatherings for catecehsis. The meeting would be presided over by a clergy member and would be open to all the congregation (Jungmann 1959, 107). Evening prayer services with a meal were also customary at this time. While times of persecution would interrupt the practice, it would resume when the persecution died out (Jungmann 1959, 108).