Since as early as about 180 A.D., the early Church used lectionary readings–an ordered system of selected readings of Scripture–in the worship services of the Church. Since at least as early as 325 A.D., specially selected Scripture portions were read aloud on the major feast days, and on ordinary Sundays the Scriptures were read aloud in lectio continua fashion, that is, a continuous reading through the books of Scripture.
That practice of the early Church followed ancient precedent from the Jewish synagogues, which had fixed Scripture readings for the Jewish feasts, as well as readings chosen for ordinary Sabbaths on the principle of lectio continua. This may have been the practice when, at the synagogue in Nazareth, Jesus “stood up to read the lesson and was handed the scroll of the prophet Isaiah” (Luke 4:16-17 NEB).