Vampires also have a mystical aversion to entering any human dwelling place which they have not been verbally invited. Once invited, they may enter the place anytime thereafter.

"He may not enter anywhere at first, unless there be some member of the household to bid him to come; though afterwards he can come as he pleases." - Professor Van Helsing in Mina Harker's Journal, Chapter XVIII of Dracula by Bram Stoker

In the original myths and folk beliefs, we find this interesting quotation from a text by Father Leone Allaci, originally published in 1645, concerning the beliefs on his native Greek island, Chios:

"For very often, inhabiting this body, he [the devil] comes forth from the grave, and going abroad through villages and other places where men dwell, more especially at night, he makes his way to what so ever house he will, and knocking upon the door he calls aloud by name in a hoarse voice one who dwells within. If such a one answers he is lost; for assuredly he will die the next day. But if he does not answer he is safe. Wherefore in this island of Chios all the inhabitants, if during the night they are called by anyone, never make reply the first time. For, if a man be called the second time it is not the vrykolakis who is summoning him but somebody else."

The Vampire in Europe by Montague Summerson page 224

A Romanian variation of this latter belief is given by Agnes Murgoci in her article "The Vampire in Roumania" in Folk-Lore, vol. 37, no. 4 (Dec., 1926):

"At anytime of the year it is well, especially at night-time, never to answer until someone calls you three times, for vampires can ask a question twice but not three times. If you reply when they speak to you, they may turn your mouth askew, make you dumb, cut off your foot, or kill you."