Tafsiran Ulangan 24:20: Rashi, Chizkuni, Ibn Ezra & Kli Yakar

לא תפאר — This means: thou shalt not entirely remove its (the olive tree’s) glory (תפארת) from it, i.e., its fruit (Chullin 131b). Hence they (the Rabbis) derived the law that one must leave פאה (some quantity of fruit) also on fruit-trees for the poor (cf. Mishnah Peah 4:1).

לא תפאר, “do not go over the boughs again,” (to look for something you had not noticed the first time.) (According to Ibn Ezra, we find the word פארות in Ezekiel 17,6: where it means “branches pointing upwards” which would eventually bear fruit. [If so, our verse would instruct the owner of the orchard not to harvest every last branch so that in the next year the tree would have difficulty in regenerating itself. Ed.]

When you shake Compare “threshing wheat” [Judges 6: 11], where the verb appears in the qal form. In “beaten out with a staff” [Isaiah 28: 27] the same verb appears in the nif‘al form.

אחריך BEHIND THEE — This implies שכחה (forgotten fruit; that if he forgets to remove some fruit from the orchard, he must leave it for the poor).