Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
set, sit (vv.)
The sun sets, and so does concrete. Hens set or sit, but judges and the rest of us sit. And when we set something down, it just sits there. Standard English uses sit as the intransitive, set as the transitive verb (although we do sit horses—i.e., “have a certain posture in the saddle”). Substandard dialects have long confused sit and set, and many Standard users consider the fault a shibboleth that indelibly brands the Vulgar speaker. The principal parts are sit, sat, sat (intransitive) and set, set, set (transitive).
