A chair for Elijah the Prophet is set up at every bris next to where the sandek sits. According to the text of the brit milah service, this chair is set up in honor of Elijah the Prophet who represents the coming of eternal peace. Traditionally the baby, carried by the kvatter or the kvatterin, is “dipped” into the Chair of Elijah before being handed to the sandek.
By Musée d’Art et d’Histoire du Judaïsme – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41923909
Why is this chair set up?
The rationale for this comes from the Book of Kings where it is seen that Elijah, after preaching to his Jewish neighbors, becomes frustrated at their lack of obedience to God’s laws as stipulated in the Torah. At one point Elijah retreats to a cave and calls out to God (Kings 19:14):
The Israelites have rejected your Covenant, torn down your altars, and put your prophets to death with the sword. I am the only one left, and now they’re trying to kill me too.
But God scolds Elijah, telling him to return and serve the people whose prophet he is (Kings 19:15):
Go back the way you came.
The dual customs of setting aside a chair for Elijah the prophet at every bris and of putting out a cup of wine for Elijah at every Passover Seder are supposedly a rebuke to Elijah, showing his eternal spirit that although the people to whom he preached disobeyed God’s laws then, Jews throughout the centuries have in fact continued to follow God’s precepts by celebrating traditions and holidays such as the brit milah ceremony and the Passover Seder.
The Chair of Elijah is set up to the right of the sandek’s chair according to the Talmudic dictum that” a student walks to the left of his teacher”, Elijah in this case being considered the teacher. Formerly in many European synagogues the congregation had a purpose-built double chair, combining seats for Elijah and for the sandek. Examples of these can often be seen at Jewish museums.