Thomas Wood, Practical Grammar and Composition
“ Do not use incorrect contractions of the verb with not. Don't cannot be used with he or she or it, or with any other singular subject in the third person. One should say, He doesn't, not he don't; it doesn't, not it don't; man doesn't, not man don't. The proper form of the verb that is being contracted in these instances is does, not do. Ain't and hain't are always wrong; no such contractions are recognized. Such colloquial contractions as don't, can't, etc., should not be used at all in formal composition. ”
