The Levoyas Chen cites a Medrash (Parsha 46) which learns from the pasuk, בעצם היום הזה נימול אברהם, that Avraham Avinu was only commanded to perform milah on this day, therefore, the milah was considered bizmanoi.
The Madanay Asher cites the Chazal that Hashem helped Avraham Avinu with the bris, therefore, it was shenayim she’osu [an act carried out by two people], which is mutar to do on Yom Kippur.
Another answer the Madanay Asher brings is based on another Medrash, which brings that a scorpion came and bit the makom hamilah. The Chida brings a remez to the above, בעצם היום הזה נימול אברהם בעצ"ם ר"ת בעקיצת עקרב צדיק מל. According to the above, there is no question.
3) The Gemara in Berachos (57b) says: “One who sees a lion’s den or a fiery furnace should make the beracha of she’oseh nes le’avoseinu bemokam hazeh [performed miracles for our forefathers in this place]”. Rashi explains, “upon seeing the furnace where Chananya, Mishael, and Azariah were thrown”. From Rashi it seems that one only makes a berachah upon seeing the fiery furnace of Chananya, Mishael, and Azariah, and not upon the fiery furnace that Avraham Avinu was thrown into.
The Shulchan Aruch (Orach Chaim 218:7) also writes: “One who sees the lion’s den of Doniel, or the fiery furnace of Chananya, Mishael, and Azariah should recite the berachah of she’oseh nes le’avoseinu bemokam hazeh” and makes no mention of the furnace of Avraham. Why is the furnace of Avraham not mentioned? And is it in fact different?
The Elyah Rabbah (Orach Chaim 218:7) answers: It’s obvious that on the fiery furnace of Avraham one needs to make a berachah, as we are all descended from him, therefore there was no need to mention it.
The Kisvei Radal (mentioned in Kuntros Migdal Dovid, which was printed in Yeshurun, year 5759, pg. 522) writes, that the reason it’s not mentioned is because it no longer exists.
