Midrash halakha (Hebrew: הֲלָכָה) was the ancient Judaic rabbinic method of Torah study that expounded upon the traditionally received 613 Mitzvot ("laws") by identifying their sources in the Tanakh (Hebrew Bible), and by interpreting these passages as proofs of the laws' authenticity. Midrash more generally also refers to the "non-legal" interpretation of the Tanakh (aggadic midrash). The term is applied also to the derivation of new laws, either by means of a correct interpretation of the obvious meaning of scriptural words themselves or by the application of certain hermeneutic rules.
Read more about Midrash Halakha: Terminology, The Midrash of The Earlier Halakha, Contrast With Earlier Halakha, Abstract and Midrash Halakha, The Two Schools