“The Lord said to Moses: Write for yourself these matters, as according to these matters I established a covenant with you and with Israel” (Exodus 34:27). “Write for yourself these matters,” that is what is written: “I write for him the many teachings of My Torah, but they are regarded as foreign” (Hosea 8:12). When the Holy One blessed be He revealed Himself at Sinai to give the Torah to Israel, He said it to Moses in order: Bible, Mishna, Talmud, and aggada, as it is stated: “The Lord spoke all these matters” (Exodus 20:1); even what a student asks his teacher, the Holy One blessed be He said to him at that time.
After [Moses] learned it from the mouth of the Holy One blessed be He, He said to him: ‘Teach it to Israel.’ He said to Him: ‘Master of the universe, I will write it for them.’ He said to him: ‘I do not wish to give it to them in writing, because it is revealed before Me that idolaters are destined to rule over them, and take it from them, and they will be despised among the idolaters.1The idolators will force the Jews to translate the Written Torah for them.
Later, they will claim that they are the true Israelites, as they also have the Torah (Midrash HaMevoar; see Pesikta Rabbati 5:1). Rather, I will give them the Bible in writing, and I will give them the Mishna, Talmud, and agadda orally, so if the idolaters come to them and subjugate them, they will be distinct from them.’ He said to the prophet: If I write for them the many teachings of My Torah, they will be regarded as foreign.2The verse in Hosea is understood to mean: If I write down the entire Torah, Israel will be regarded as foreigners.
What will I do for them? I will give them the Bible in writing, and the Mishna, Talmud, and agadda orally [al peh]. “Write,” this is the Bible; “as according to [al pi] these matters” (Exodus 34:27), these are the Mishna and the Talmud, which distinguish Israel from the idolaters.