By this time the collection of halakhic material had become very large and various, and after several attempts had been made to reduce it to uniformity, a code of oral tradition was finally drawn up in the and century by Judah ha-Nasi, called Rabbi par excellence.
Of this halakhic Midrash we possess that on Exodus, called Mekhilta, that on Leviticus, called Sifra, and that on Numbers and Deuteronomy, called Sifre.
The material thus accumulated, both halakhic and agadic, forming a commentary on and amplification of the Mishnah, was eventually written down under the name of Gemara (from gemar, to learn completely), the two together forming the Talmud (properly "instruction").
Individual Geonim produced valuable works (of which later), but what is perhaps most important from the point of view of the development of Judaism is the literature of their Responsa or answers to questions, chiefly on halakhic matters, addressed to them from various countries.
Of the same school were Menahem ben Simeon of Posquieres, a commentator, who died about the end of the 12th century, and Moses ben Jacob of Coucy (13th century), author of the Semag (book of precepts, positive and negative) a very popular and valuable halakhic work.