Midrash is Judaism's homily: stories told to deliver a lesson.

And that is not just my apikorsus (heresy) coming through, it is an accepted tenet of even orthodox scholarship and of the Midrash itself that the stories recorded in it did not really happen. For instance, the Midrash says that when the Jews were at Mount Sinai receiving the Torah, God picked the mountain up and held it over their heads, threatening to kill them if they didn't accept the Torah. The Midrash is not trying to convince its audience that this incident actually happened, its merely conveying the message the the Jews had to accept the Torah, this had been the urgent destiny of the universe since its creation.

One major tenet of the Midrash is that every word, letter, and puctuation mark within the written Torah appears for a reason. Because the Bible was written by God, it contains a perfect economy of language where each written symbol signifies a deep intrinsic message. The Midrash is often guilty of finding prooftexts simply to insert its lessons into. A verse in question will serve as a mnemonic by which to remember the lesson, though it obviously does not bear that meaning when examined in context. (Incidentally, I've seen this method applied by Christian missionaries on a lesser scale, lifting verse from the Book of Isaiah and applying them to the yet unborn Jesus.) The Midrash can seem to be a commentary on the written Torah, but it isn't. It is fixated on verses, words, and letters, but never the bigger picture.

There are fundamental lessons about the nature of Judaism buried in the seemingly fantastic stories of the Midrash. In fact, the word "midrash" come from the root D-R-SH, which means to search. In this case, the written Torah is being plumbed, word by word, sometimes letter by letter, for lessons. Dogma claims that as a section of the oral law, the Midrashim were delivered to Moses by God at Mount Sinai, and were transmitted verbatim for generations, until being written down in the Middle Ages. God needed to provide Moses with the Midrash as an explication for the lessons hidden in the Bible: "The Bible, or written law, contains unexplained passages and hidden sentences, which can not be fully understood without the help of the oral law."

The material that constitutes the Midrash in fact arose between 400 BCE and 500 CE- earlier than the Middle Ages but later than Mosaic times. The Mechilta, Sifra and Sifrei collections are particularly ancient. Between 300 and 1200 CE, contemporaniously with and following the incorporation of the Talmud, a similar process was employed to record the orally circulating legends that were the Midrash, which were written down in a mixture of Hebrew and Aramaic. Working alone, Rabbis would resolve to collect all of the Midrashim that they had been taught commenting on a particular book of the Bible, and whoever copied the resulting manuscript would add what he had been taught, the next copier would add a bit as well... leading to an overlaping codus of books.

There are two types of Midrash- Midrash Aggadah and Midrash Halachah. The former is more common and consists of stories, while the latter is a legal explication of Biblical laws. Both of these exist side by side within the Midrashic texts, however some volumes have a greater proportion of one or the other. A number of the early Medieval Biblical exegites quote the Midrash in their commentaries, particularly Rashi.

Some books of the Midrash are: There some English translations of the Midrash, including one of Midrash Rabba published by Soncino. There are a large number of English Midrashic digests, books containing a smattering of Midrashim. Normally I'd object to this porcess, however the Midrash was never anything other than fragmented legends taken out of context, so the further isolations of the most attractive stories can hardly be condemned. For the full English texts of some of the books of Midrash, see http://www.sacred-texts.com/jud/mhl/index.htm