What does the Mitzvah of "Lo Se'olel" entail?
Rashi: It is a La'av against picking from the vine deficient clusters that contain neither 'shoulders' nor 'Netef'. 1
Rashi (citing Yerushalmi, Pe'ah, 9:7): Shoulders are tightly-packed rows of grapes resting one on top of the other (Sifsei Chachamim). Netef are grapes that hang from the spine.
Why does the Torah add the word "Lo Se'olel Acharecha'"?
Chulin, 131a: To teach us, via a Gezeirah Shavah "Acharecha" "Acharecha" ? in Pasuk 29 ? that all trees are subject to Pe'ah.
Chulin, 131b: To incorporate trees in the Din of Shikchah.
Why does the Torah write "Ki Sivtzor Karm'cha Lo Se'olel" and not simply "Lo Sivtzor Olelos Karm'cha"?