The thirteen hermeneutical rules of Rabbi Ishmael

The thirteen middot ("measures") of Rabbi Ishmael are the hermeneutical principles by which the Oral Law derives rulings from the written Torah. They include a fortiori reasoning (kal vachomer), verbal analogy (gezerah shavah) and inference from the general and the particular. Stated at the beginning of the Sifra, they are recited in the morning liturgy and underpin halakhic reasoning.