A sign, saying or image that anticipates, sometimes only for the rereader, something that will happen later in the work.
In White Nights
do not fall in love with me... That cannot be, I assure you.
“That cannot be, I assure you” anticipates what will happen: he falls in love, and the love will have no place. The prohibition spoken on the first night is fulfilled, as impossibility, in the declaration of the fourth.