In the previous post in this series we discussed the necessity of the Oral Torah. In this post we will begin exploring the criteria by which a law was part of the written or oral Torah. This question is two-fold: 1) why are certain halakhot explicit in the Torah while others are received traditions and halakhot l'moshe m'sinai, 2) why are certain halakhot explicit in the Torah (p'shat) while others are derived from interpretation (derasha). The following is based on Kedushat Peshuto shel Mikra by R. Yehuda Cooperman; however these points require a tremendous amount of further study and elucidation. In a later post we wil discuss this question regarding the narrative sections of the Torah.
This question is not merely theoretical since there are halakhic implications between the written and oral law. For example, the Sages cannot make a derasha on a received tradition. See Tos. Moed Katan 4:1 and Ri m’Paris there; Rashi Sukkah 34a.
1) The written Torah presents the mitzvah in its eternal state. It may not be changed. A kal v’chomer or gezera shava could change. See Sota 5:2; Ketav v’Hakaballah, Devarim 23:3; Dor Rev’i, Hakdama.
2) The written Torah reveals and clarifies the nature of the halakhah. From it we can clarify the halakhah. See Hakdama to Vayikra of the Netziv; Netziv on Shemot 21:26 and Rambam, MN 3:26; Seforno on Shemot 23:19.
3) The written Torah may teach the l’chatchila din. See Rosh on BK 7b; Ritva on Yevamot 103b.
4) The punishment (bidei shamayim) is more stringent for something explicit in the Torah (as opposed to a kabbalah, gezerah shava etc.). See Netziv Vayikra 19:27 and 13:45.
5) The primary purpose of the written Torah is not a legal text but a mystical text. See Shiurei Da'at vol. 1, pgs. 243, 263 and vol. 2 pg. 101