How can the Torah mention Kush and Ashur, seeing as the world had not yet been built?
Rashi: The Torah mentions the names by which they were destined to be called in the future.
QUESTIONS ON RASHI
Rashi writes: "'Kush;' 'Ashur' - The verse is using terms [that would be relevant] in the future." We could have explained that by the time when Moshe wrote down the Torah, the nations of Kush and Ashur already existed?
Gur Aryeh: The events of the Torah are narrated as they occurred at the time, not as historical events of the past. 1 The Torah does not begin with, 'These are the words of Moshe.' Rather, we need to explain that here, the verse is using terms that would be relevant in the future.
Rashi writes: "The verse is using terms [that would be relevant] in the future." But perhaps the region was known as "Ashur" ever since Creation, and the individual known as Ashur (10: 11,22) was named after the region?
Gur Aryeh: It is illogical to call one person after a region, for what distinguishes that one person from everyone else who was born there? On the contrary, a region should be named after the person who built it up.
Rashi writes: "'Kush;' 'Ashur' - The verse is using terms [that would be relevant] in the future." Why doesn't Rashi explain the same regarding "Chavilah" (2:11)?
Gur Aryeh: While Ashur and Kush can be proven to be named after the people known by that name (see Gur Aryeh), we cannot prove the same regarding Chavilah. 1
Rashi writes: "'Kidmas Ashur' - To the east of Ashur." What is Rashi clarifying?
Mizrachi: Grammatically, the letter 'Sav' at the end of "Kidmas" comes in place of a suffix, "Hei," meaning "to," which is changed to a 'Sav' due to its construct state. Hence, "to the east of Ashur." 1
Gur Aryeh: As opposed to 'mi'Kedem,' which would mean 'directly to the east,' the word "Kidmas" means "on the east side." 2
Rashi writes: "'The Euphrates' (Peras) - It is the most important of all [the rivers]." How do we know that it is most important; perhaps it is the largest?
Gur Aryeh: If it was the largest of the rivers, it should have been listed first.