Kelim, Chapter Five, Mishnah Ten
1) If he cut the oven up into rings, and then he put sand between each pair of rings, Rabbi Eliezer says: it is clean.
a) But the sages say: it is unclean.
b) This is the oven of Akhnai.
2) As regards Arabian vats, which are holes dug in the ground and plastered with clay, if the plastering can stand of itself it is susceptible to impurity;
a) Otherwise it is not susceptible.
b) This is the oven of Ben Dinai.
Section one: In this case a person took an oven and cut it into rings, and then reassembled it, filling in with sand in between the rings. He then coated it all over with clay and heated it up so that it would be usable.
Rabbi Eliezer rules that such an oven is not susceptible to impurity because of the presence of the sand between the rings, whereas the sages hold that the coating makes the oven into one unit and therefore it is susceptible.
This oven is known as “the oven of Akhnai,” which probably refers to the manufacturer of the oven. The Talmud’s famous tale of the argument between Rabbi Eliezer and Rabbi Joshua is told concerning this oven. In this tale Rabbi Eliezer calls upon God to break the laws of nature to prove that his position is correct, and the miracles indeed occur. Rabbi Joshua responds “it is not in Heaven,” meaning that after God gave the Torah to Israel, the law is no longer in Heaven, but rather subject to the independent interpretation of human beings. This is a foundational story for the rabbis, for it substantiates their understanding of Torah interpretation.
Section two: An “Arabian vat” is simply a hole dug in the ground whose walls are covered with plaster. If the plaster can stand on its own, then the oven is susceptible to impurity, but if it requires the earth to support it, then it is not susceptible. This oven is called the oven of “Ben Dinai.” Some hold that Ben Dinai was a robber who would bake his bread in such an oven. Others hold that “Ben Dinai” comes from the word “din” which is Hebrew for either logic or law. It was called “Ben Dinai” because there were debates over such an oven.