Elijah the Prophet

At many brisses, two chairs are set up at the spot where the bris itself will take place. Ask the mohel, he'll tell you "One is for the sandak (who holds the baby during the bris), and the other is for Eliyahu Hanavi (Elijah the prophet)."

You're kidding, right?

No. The tradition to have a place set aside for Elijah at a bris is pretty old.

It is recorded in the Shulchan Arukh (Code of Jewish Law) in Yoreh Deah 265:11

שולחן ערוך יורה דעה סימן רסה

נוהגין לעשות כסא לאליהו, שנקרא מלאך הברית, וכשמניחו <יב> יאמר בפיו שהוא כסא אליהו

 "There is a custom to set up a chair for Elijah, who is called the "Angel of the Bris," and when you set it up, declare that it is the chair of Elijah."

And the Gaon of Vilna comments there, quoting the tale as recorded in Pirkei D'rabi Eliezer, chapter 28 (translation below):

פרקי דרבי אליעזר - "חורב" פרק כח
ויעש לו יהושע חרבות צורים וקבץ את כל הערלות עד שעשה אותם כגבעה, וימל את בני ישראל אל גבעת הערלות, והיו ישראל לוקחים את הדם ומכסין אותו בעפר המדבר, וכשבא בלעם ראה את כל המדבר מלא מערלותיהם של ישראל אמ' מי יוכל לעמוד בזכות דם ברית מילה זאת שהיא מכוסה בעפר הארץ, שנ' מי מנה עפר יעקב, מכאן התקינו חכמים שיהיו מכסין את הערלה ואת הדם בעפר הארץ, שנ' והיה זרעך כעפר הארץ, וכך היו ישראל נהוגים למול עד שנחלקו לשני ממלכות ומלכות אפרים נמנעה מהם ברית מילה ועמד אליהו זכור לטוב וקנא קנאה גדולה ונשבע לשמים שלא להוריד טל ומטר על הארץ ושמעה איזבל ובקשה להרוג אותו ועמד אליהו והיה מתפלל לפני הב"ה, ואמ' לו הב"ה אליהו טוב אתה מאבותיך ברח, עשו בקש להרוג את יעקב וברח מלפניו, שנ' ויברח יעקב, פרעה בקש להרוג את משה וברח ונמלט מלפניו, שנ' וישמע פרעה את הדבר הזה, שאול בקש להרוג את דוד וברח מלפניו ונמלט, שנ' אם אין אתה ממלט את נפשך, וכתיב אחר אומ' ודוד ברח וימלט, למד שכל הבורח נמלט ועמד אליהו ז"ל וברח לו להר חורב, שנ' ויקם ויאכל וישתה, ושם נגלה לו הב"ה אמר לו מה לך פה אליהו, קנא קנאתי, אמ' לו לעולם אתה מקנא, קנאת בשטים על גלוי עריות, שנ' פנחס בן אלעזר בן אהרן הכהן, וכאן קנאת, חייך שאין עושין ברית מילה עד שאתה רואה בעיניך, מכאן התקינו חכמים לעשות כסא אחד מכובד למלאך הברית, שנקרא אליהו ז"ל מלאך הברית, שנ' ומלאך הברית אשר אתם חפצים.

Joshua needed to make flintstones [for circumcision] on account of the fact that those who had been circumcised had not removed the lower membrane (עור הפריעה, or ha'priah) [and they did not look circumcised], and he gathered all the foreskins in the "Valley of the Foreskins." The Isrealites would take the blood [of the circumcision] and cover it with the dust of the desert. When Bilaam came, he saw the desert filled with the foreskins of the Jews and he said "Who could stand against the merits of the blood of the covenant, which is covered with the dust of the earth?" – as he said (Numbers 23:10) "Jacob [is like] the dust; who can count his [hordes]?"

From here the rabbis established the rule that the blood and the foreskins should be covered with dirt* - following the dictum that "Your children will be like the dust of the earth" (Genesis 28:14).

And this is how Israel practiced bris milah, until they were divided into two kingships (Kings I), when the Kingdom of Ephraim outlawed Bris Milah. Elijah stood up to them, jealous on God's behalf, and zealous against the forsaking of God's Torah and lifestyle. He swore that the heavens would not produce rain. [There was no rain on account of this for several years] [Queen] Izevel heard about his declaration and wanted to kill him, and Elijah stood and prayed to God. God told him he was following the precedent established by his ancestors. Jacob fled from his brother Eisav, who wanted to kill him. Moses fled from Pharaoh, who wanted to kill him. David fled from Saul. Elijah therefore fled and ran to Mt Horeb. (Kings I 19) God revealed Himself to Elijah there, saying "What are you doing here Elijah?" And Elijah said "I have acted with great zeal for God. [but the people of Israel have forsaken Your covenant]" God said, "You are always acting with zeal. You acted zealously against immorality at Shitim [as Pinchas]**, and now you act with zeal. I swear that a bris milah will not take place until you see it with your eyes." From here, the rabbis established the custom that we arrange a chair for Elijah, the angel of the bris. The term "Angel of the bris" comes from Malachi 3:1, in a discussion that concludes with the promise of the sending of Elijah as the Messiah at the end of days.

* While it is hard to gather blood that is absorbed in gauze pads and bandages, it is proper practice to bury the foreskin after the bris.

** There is a tradition that Elijah was either a reincarnation of Pinchas (Yalkut Shimoni 771, Midrash Aggadah Bamidbar 25:13) , or was the same man with a different identity (obviously the first approach is more plausible because otherwise he'd be hundreds of years old)

AND THEREFORE

 
The custom is to set aside such a chair, and to make a bit of pomp and ceremony surrounding the presence of Elijah at the bris.
 
Elijah's presence is also noted at the seder, and I will write about the connections between Passover and Bris Milah in a different posting.
 
Suffice it to say, Elijah's presence is also the source for a different custom related to the bris, and that is to avoid "inviting people."
 
I wrote this a long time ago:

There is an old custom not to "invite" people to a bris due to the belief that the spirit of Elijah the prophet is in attendance. Were people to be invited and not come, this would seem as an affront to the prophet. But if they are merely informed that "the bris will take place at such and such time and place" they are not declining any invitation if they don't show up.

Lastly, I quote a thought that was shared with me by Rabbi Perry Tirschwell in the name of Rabbi Menachem Genack:

Eliyahu's role is the guardian of the mesora. He represents the authenticity- the link in the chain back to Moshe. Kano kinasi l'hashem - he was the voice of tradition.

Therefore,...

• He shows up at a bris- when we bring a newborn into the tribe.
• He is m'taretz kushyot v'abayot (as opposed to Moshe Rabbeinu) - he's the link back.
• He comes to the seder- the moment of mesora from one generation par excellence.
• He is the harbinger of Moshiach - he'll know who's real and not real.

Eliyahu's work was not done when he was swept up on a chariot - he is needed in every generation to give the nod of approval that though we may look different, and our lives are vastly different than our ancestors, that we are still keeping the faith.

The person who places the baby on this chair, therefore, is considered to have a significant role - bringing the baby as close to one of the greatest defenders of the covenant, whose soul, it is believed, will one day inhabit the body of the Messiah.