Берешит 2:14 Комментарий: Rashi, Chizkuni, Radak & Siftei Chakhamim

חדקל TIGRIS — It is called חדקל because its waters are pungent in taste (חד) and light in weight (קל) (Berakhot 59b).

קדמת אשור, the letter ת at the end of the word: קדמת is in lieu of the letter ה, as in קדמה. Sometimes the Torah also uses the letter ה as a suffix instead of the letter ל as a prefix as in למזרח אשור “east of Ashur.”

ושם הנהר השלישי...קדמת אשור, it flows more or less in a continuous direction to the eastern region of what was the land of Ashur at the time the Torah was given. It does not circumvent that country but flows in a northerly direction, seeing that both Babylon and Ashur are situated north of Gan Eden. [In order to make even partial sense of all this, it helps to understand such definitions as “northerly, southerly, easterly,” as relative to the location of Eretz Yisrael, not as relative to the north and south poles of our globe. Rashi already found it necessary to describe the river Nile as running underground for a considerable distance in order to make the Biblical report compatible with the facts as known in his time, much earlier than Kimchi. Ed.] חידקל, this river is so called because its waters are clear and flow rapidly (Berachot 59).

פרת EUPHRATES — It is called פרת because its waters grow (פרה) and increase and make men healthy (Berakhot 59b). כוש ואשור CUSH AND ASHUR did not then exist as countries, but Scripture writes with reference to the names which those districts would bear in the future (Ketubot 10b; Genesis Rabbah 16).

קדמת אשור means AT THE EAST OF ASHUR.