Midrash primarily directed to the clarification of legal issues. This term is usually used to designate the tannaitic midrashim on the last four books of the Pentateuch, which also contain varying proportions of Midrash Aggadah. Thus the Sifra is almost exclusively halakhic (legal), while Mekhilta De-Rabbi Ishmael is slightly more than half aggadic.
A number of indications point to an ancient common source from which the editors drew their material. The identical exposition (Derash) appears in a number of the tannaitic midrashim. Since this common ancient source was taught in the various schools, each one left the mark of its own terminology and method on the material. The midrashim that come from the School of R. Ishmael favor deriving legal decisions by Hermeneutics. Those that stem from the school of R. Akiva prefer to derive the law by expounding the biblical text.
Current scholarly opinion maintains that there is no positive evidence that the sages of the Talmud drew directly on midrash halakhah, though some scholars maintain that the Talmud does quote the tannaitic midrashim directly. The Tosefta quotes extensively from the halakhic midrashim.
Midreshé halakhah from the school of R. Ishmael are: Mekhilta de-Rabbi Ishmael on Exodus; fragments on Leviticus; Sifré Numbers on Numbers; and Sifré Deuteronomy on Deuteronomy. The corresponding works from the school of R. Akiva are Mekhilta De-Rabbi Simeon; Sifra; Sifré Zuta; and Midrash Tanna'im.
