Hath is simply has — the old form for he, she, or it. “She hath a kind heart” means “she has a kind heart.” Nobody uses it in normal talk now, except when quoting the Bible, Shakespeare, hymns, or a historical play. It is not “more polite” has; it is costume-English. In old grammar the ending -th did the same job that -s does today (he hath / he has; he doth / he does). You may still see hath on old signs or in set phrases, but in class, emails, and conversation, say has.

has 的古體（他／她／它「有」；聖經、莎士比亞常見）