וְלֹֽא־יִוָּדַ֤ע הַשָּׂבָע֙ בָּאָ֔רֶץ מִפְּנֵ֛י הָרָעָ֥ב הַה֖וּא אַחֲרֵי־כֵ֑ן כִּֽי־כָבֵ֥ד ה֖וּא מְאֹֽד׃
Und man wird im Lande nichts von dem Überfluss merken infolge der Hungersnot, die kommen wird; denn sie wird sehr drückend sein.
Rashi on Genesis
ולא יודע השבע AND THE PLENTY SHALL NOT BE KNOWN — this is the interpretation of (v. 21) “And it could not be noticed that they had eaten them up”.
Siftei Chakhamim
This is the interpretation of “But it could not be recognized...” You might ask: [Rashi says that ולא יודע השבע is the interpretation of the good cows being eaten up.] Why did Rashi not explain that ונשכח כל השבע is the interpretation of the good cows being eaten up? Rather, he says [on v. 30] that ונשכח כל השבע is the interpretation of the ears of corn being swallowed up. The answer is: ולא נודע כי באו אל קרבנה, said of the cows in v. 21, is from the root of הודעה, and so is ולא יודע השבע here. Therefore, Rashi connects them. However, ונשכח is not from הודעה, therefore Rashi connects it with the ears being swallowed up.