פירוש על דברים 24:20

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).

Do not remove its glory from it, etc. Meaning, that you may not remove all its fruit to the point that its glory does not remain. The expression לא תפאר [where the word “glory” means to remove the glory] is similar to the expression, “ כל תבואתי תשרש (It would root out all my produce) (Iyuv 31:12),” which means to uproot [even though תשרש means to take root].