Orthodox Judaism holds that on Mount Sinai, the Written Law was transmitted along with an Oral Law. The words of the Torah (Pentateuch) were spoken to Moses by God; the laws contained in this Written Torah, the "Mitzvot", were given along with detailed explanations in the oral tradition as to how to apply and interpret them. Furthermore, the Oral law includes principles designed to create new rules. The Oral law is held to be transmitted with an extremely high degree of accuracy. Jewish theologians, who choose to emphasize the more evolutionary nature of the Halacha point to a famous story in the Talmud, where Moses is miraculously transported to the House of Study of Rabbi Akiva and is clearly unable to follow the ensuing discussion.
Who spoke the words of the Torah to Moses?
God