Musar sobre Génesis 4:3

פשתן, flax, and צמר, wool, are the mystical dimensions of Cain and Abel respectively. History has taught that the two, i.e. Cain and Abel, did not mix successfully.

The flax and camels in the story in the Tanchuma that we quoted are metaphors. The example of the camels laden with flax refers to Cain, whose sacrifice (the one G–d rejected) consisted of flax (Tanchuma Bereshit 9). The example of the camel is a metaphor for Esau who had said to Jacob: הלעיטני נא מן האדום האדום הזה (Genesis 25,30). The expression הלעיטני is reminiscent of camels as we know from Shabbat 155, that whereas one must not stuff a lot of food down a camel's throat (on the Sabbath), one may feed it by a method called מלעיטין. The reason that Rabbi Levi in Bereshit Rabbah used the metaphor of קוצים, thorns, is because G–d told Adam after he had eaten from the tree of knowledge that the earth would respond to his efforts by bringing forth קוץ ודרדר, thorn and thistle (Genesis 3,17).