With regard to Torah, Rav Huna related that Rav said: The Torah is destined to be forgotten from the Jewish people. It is stated at the conclusion of the curses in the Torah’s reproof: “And the Lord will make your plagues astonishing, and the plagues of your seed, great plagues of long continuance, and evil diseases of long continuance” (Devarim 28:59). This term of astonishment, mentioned in the verse in addition to the explicit punishments, I do not know what it is. But when the verse states elsewhere: “Therefore, behold, I will continue to astonish this people with wondrous astonishment, and the wisdom of its wise will be lost, and the understanding of its men of understanding shall be hidden” (Yeshayahu 29:14), you must say: This astonishment is referring to forgetting the Torah.
Some commentaries explain Rav’s statement as follows: The Torah is destined to be forgotten if the Oral Law is transmitted by word of mouth, rather than being written down. Therefore, it is imperative to commit the Oral Law to writing to prevent it from being forgotten (Korban Netanel).
The Sages taught a similar idea in the Tosefta: When our Sages entered the vineyard in Yavne, they said: The Torah is destined to be forgotten from the Jewish people, as it is stated:
“Behold, days are approaching, says the Lord God, and I will send forth a hunger in the land, not a hunger for bread and not a thirst for water, but for hearing the words of the Lord” (Amos 8:11). And it states: “And they will drift from sea to sea, and from north to east they will roam to find the word of the Lord, but they will not find it” (Amos 8:12).
“The word of the Lord” in this context bears many meanings. “The word of the Lord”; that is halakha. “The word of the Lord”; that is the end of days. “The word of the Lord”; that is prophecy. All these will be lost from the Jewish people.
Since “It is the honor of God to conceal a matter [haster davar]” (Mishlei 25:2), and the end of days is known to God alone and to no one else, this statement should be interpreted to mean that the word of God [devar Hashem], i.e., that which is uniquely His, is referring to the end of days (Iyyei HaYam; Ein Ya’akov).