What are the implications of "Va'yavei Kayin mi'Peri ha'Adamah"?
Rashi #1: It means that he brought inferior-quality fruit. 1
Rashi #2: The Korban that he brought comprised flax-seeds (which is an inferior species).
Rashi #2: He did not take the trouble to pick something to bring as a Korban to Hashem, but brought whatever came to hand.
Hadar Zekenim: and Moshav Zekenim: It means that he brought from the leftovers of his food.
See Sifsei Chachamim.
Regarding Noach, the Torah writes (in 8:20), "Va'Ya'al Olos ba'Mizbe'ach". Why here does the Torah call Kayin's Korban "Minchah"?
Oznayim la'Torah: This goes well with Rashi, who writes in Parshas Emor (Vayikra 24:9) that whatever comes from produce (that grows from the ground) falls under the category of Minchah. 1
Oznayim la'Torah: And having called Kayin's Korban 'Minchah', it also refers to the Korban of Hevel as 'Minchah'. See Oznayim la'Torah.
QUESTIONS ON RASHI
Rashi writes: "'From the fruit of the earth' - of the worst quality". How is this derived from the Pasuk?
Gur Aryeh: The Pasuk adds the term "from the produce;" meaning a distinct subset of it (in this case, in terms of its inferiority). 1
Sifsei Chachamim: Because otherwise, the Torah should have inserted the word 'me'Reishis Peri ha'Adamah'. 2
Rashi writes: "[Kayin brought] of the worst quality." If Kayin wanted to bring a Korban of his own initiative, why did he choose his worst produce? The entire world was at his disposal!
Gur Aryeh #1: Kayin's personal trait was Ayin Ra'ah (jealousy, stinginess). Through his inferior Korban, he aimed to strengthen his personal trait, and to use it to overpower Hevel.
Gur Aryeh #2 (later in this verse): Kayin wanted to bring the opposite of Hevel's offering, as a reflection of himself - and even if that poor offering would reflect the earth's curse, so be it.
Rashi writes: "A Midrash says that it consisted of flax-seed". What is the source for this in the Pasuk?
Mizrachi: If one spells out the letters of the word "Korban", 1 the last letters of each name spell "Pishtan", flax.