Комментарий к Дварим 33:14

וממגד תבואת שמש AND BY THE PRECIOUS FRUITS BROUGHT FORTH BY THE SUN — for this land lay exposed to the sun and it therefore produced sweet fruit (Sifrei Devarim 353:3).

וממגד תבואת שמש, “and from the bounty of the sun’s crop.” It is well known that the sun is closely associated with the element fire. The closer we get to the sun or vice versa, the hotter it gets. The feeling of being cold is generally associated with the distance from the sun. The heat of the sun causes crops and fruit to ripen. The moon, by contrast, is associated with the element water. Proof is the fact that it exerts influence on the oceans (beaches) determining the tides. Absence of the moon in the sky, or gradual disappearance of it, results in the waters of the sea and some rivers receding. The power of both sun and moon to affect the ripening of crops on earth is called by Moses מגד. The verse tells us that the territory of Joseph will experience the beneficial effects on its harvests of both sun and moon. The moon is perceived as מגרשת הפירות, brings the fruit of the tree to separating. [I prefer Hirsch, who sees in the word ירחים an allusion to the number of months animals are pregnant, i.e. the fruit of the womb is produced after a certain number of “moons,” Ed.]

Another interpretation. “The monthly yield.” Rashi is answering the question: It should have said גרש ירח (moon’s ripening) in the singular form. Why does it say ירחים (moons’)? He [therefore] explains, Which the earth sheds, etc. i.e., each month produces once again and therefore it is written moons’ in the plural form.