Saith means says. It is only the old form for he, she, or it — the way English used to mark “this person does it now.” Four hundred years ago a verb often took -th at the end: he hath (he has), he doth (he does), he saith (he says). You will meet it in the old Bible many churches still read, in Shakespeare, and when someone puts on a church-or-castle voice for a joke or a story. Nobody says it in a shop, a text, or a normal class. If you write he saith in an email, it sounds like a costume, not like careful English. The sound is like seth, not like say with an extra th stuck on.

（古語）說（第三人稱，等於 says）