Commentaire sur Le Deutéronome 28:40

ישל means, it (the olivetree) shall drop its fruits. It is similar in meaning to the verb in (Deuteronomy 19:5), "And the iron falleth off (ונשל).

ישל, from the root נשל as in Deut. 7,1 ונשל גויים, “He will dislodge,” the construction is parallel to that of ימל קצירו in Job 18,16 compared to Genesis 17,11 ונמלתם, you shall circumcise.” The root נשך also becomes ישך in the future tense.

Will discard its fruit, meaning the same as “And the iron discards.” Rashi is not satisfied to say that that it (ישל) means being discarded, because it is a verb applying to an object where the object, i.e., the fruits, are missing [from the sentence]. Therefore he says, “Will discard its fruit, meaning the same as 'And the iron discards (נשל),'“ which is also a verb applying to an object and means that the iron will discard a piece from the wood being hewed, and it will go and kill him. (Re”m)