Three other sermon traditions assume a text and a fixed frame: an assigned reading, a determined moment in the service, a designated speaker. A fourth history complicates that assumption from inside Christianity itself.
In April 1906, an African American holiness preacher named William J. Seymour opened a continuous revival meeting at a former livery stable on Azusa Street in Los Angeles that ran, in some form, for roughly three years. Its preaching answered to no lectionary and no fixed schedule. Services opened without a set order, testimony and spontaneous exhortation from members of the congregation stood alongside sermons from Seymour and visiting ministers, and the preaching was understood by participants as directly led by the Holy Spirit in the moment rather than prepared in advance around an assigned text, often accompanied by glossolalia, speaking in tongues, which the movement took as evidence the Spirit was actively speaking through ordinary worshippers and not only through the ordained.
The revival was also racially mixed in a way striking for Jim Crow era Los Angeles, with Black, white, Latino and Asian worshippers preaching and praying together. Missionaries carried the Azusa Street style of unscripted, participatory preaching outward within a few years, and it became a founding model for the global Pentecostal and later charismatic movements, an account of what a sermon is that runs on spontaneity and communal participation rather than on a prepared text tied to a fixed calendar.