It is necessary to prepare a seat for Eliyahu, and to verbally articulate “this is the throne of Eliyahu.” If not, Eliyahu is not present at the bris. * From Chapter 8 of Rabbi Shloma Majeski’s Likkutei Mekoros. (Underlined text is the compiler’s emphasis.)
The Seventh Precept is to circumcise the male child on the eighth day after birth, thereby removing the defilement of the foreskin. The “living” of which we have spoken forms the eighth grade in the scale, and hence the soul which departs from it must appear before it on the eighth day. In this manner it is made clear that it is truly a “living soul,” emanating from holy “life” and not from Sitra Achara.
This concept is alluded to in the words of the verse, “May the waters swarm.” The Book of Chanoch interprets these words as follows: Let the “waters” of the holy seed be stamped with an impression of “the soul of the living,” which is in the form of the letter Yud, impressed upon a holy body prior to all other marks.
The words, “And let winged creatures fly upon the earth” refer to Eliyahu, who traverses the universe in four swoops in order to be present at the initiation of a Jewish boy into the holy covenant. It is necessary to prepare a seat for Eliyahu, and to verbally articulate “this is the throne of Eliyahu.” If not, Eliyahu is not present at the bris.
(The Teachings of the Zohar for the night preceding a bris mila; Preface to the Zohar daf 13)