Biblical Unitarians hold that the biblical canon is closed and that Scripture is the complete, sufficient, and final revelation of God for human salvation and Christian living. No new revelation — prophetic, apostolic, or otherwise — supplements or supersedes the 66-book canon. This cessationist position is consistent with the movement's strong commitment to sola scriptura.

The rejection of extra-biblical revelation is integral to the Biblical Unitarian critique of Trinitarian Christianity: the doctrine of the Trinity, in their view, is precisely an example of post-biblical tradition being elevated to the level of Scripture. The solution is not new revelation but careful, unclouded reading of the existing Scriptures. Extra-biblical revelation would only add to the problem of tradition overriding the clear biblical text.

Some Biblical Unitarians may hold more open views regarding providential guidance or the Spirit's illumination of Scripture — affirming that the Spirit works through the biblical text to guide believers into deeper understanding — but this is understood as illumination of existing Scripture, not new revelation. The boundary between what Scripture teaches and what additional authorities might add is carefully maintained.