Until the Messiah comes, however, Jews believe that Elijah may pop up anywhere. At every circumcision, a chair is left empty for him. At the Passover seder, Jews leave a cup filled with wine that remains untouched for Elijah to drink. Toward the end of the seder, Jewish families all around the world open the front door to welcome Elijah into their home, hoping he will bring with him the time of redemption.
— Naomi Levy, To Begin Again