Principles of Jewish Law transmitted originally to Moshe (Moses) by G-d at Mt. Sinai, during the forty days and forty nights that Moshe was at the top of the mountain, to be transmitted from parents to children or from teachers to students. Contains explanations of the Written Law, where it is necessary, e.g. physical definition of Tefilin, and explanation of Jewish concept of an “eye for an eye,” which would otherwise be completely misunderstood. Originally, the “Oral Law” was not meant to be written down, but when the difficulties of Jewish History threatened to cause its forgetting, Rabbi Yehudah HaNasi compiled the Mishnah, and Ravina and Rav Ashi compiled the Gemara.