Catholics, Episcopalians, and some other denominations use a lectionary, a list or table of designated Bible passages for each worship service.
The practice is very old, going back to Jewish synagogues. Bible passages are chosen to tie in with holy days such as Easter, Christmas, and Pentecost.
The theory behind lec-tionaries is that they require that a church have a public reading of key passages from the Old and New Testaments.