Epistles of Muḥammad ibn ʿAbd al-Wahhāb, the founder of the Wahhābī movement in eighteenth-century Najd, are preserved in profusion in Wahhābī sources. One of them is a short epistle, clearly intended for a lay audience, that sets out basic Wahhābī dogma in terms of four principles (qawāʿid). This epistle is preserved by Wahhābī sources in several different versions; none of them are dated, making it hard to establish how the text evolved over time. The present study is based on two dated external witnesses to the text of the epistle. One is taken from an unpublished Baṣran refutation of 1745, and is translated here. The other is found in a Yemeni chronicle under the events of the year 1212/1797f. Thanks to these two fixed points, it is possible to construct a plausible account of the evolution of the text over the intervening decades. From this it is clear that while written transmission played a significant part in the evolution of the text, some of the more dramatic changes are the result of oral intervention. Moreover the role of orality is confirmed by evidence suggesting the extensive use of the epistle in oral settings, an illustration of the strong concern of Ibn ʿAbd al-Wahhāb to spread his message among the laity.