In Parshat Kedoshim, Perek 19 Pesukim 18-19, we see two mitzvot. The first of the two is “you shall love your fellow friend as yourself”, and the second is “do not wear a garment that contains a forbidden mixture of fibers.” (We refer to this second mitzvah as Shatnez, or garments made of wool and linen.) Is this really the appropriate time to mention Shatnez? Why is it mentioned here, along with the Mitzvah of loving your fellow frined as you would love yourself?
Based on the fact that the Mitzva of Shatnez is a chok, (a mitzvah whose logic is beyond human understanding,) Rabbi Pinchas Winston offers an answer. He cites a midrash which explains a possible reason for this Mitzva. This midrash says that the reason is derived from the story of Cain and Abel.
In the story of Cain and Abel, the brothers each offer a korban to Hashem. Because Abel gave an extravagant korban while Cain’s was pretty lousy, Abel’s was accepted, and Cain's was rejected. Cain did not take this well and vented his anger by killing his brother.
Now, let us think about what each brother brought as his korban Cain was a farmer and brought flax, the worst of his crop. Abel was a shepherd and brought a sheep, the best of his flock. Since wool and flax, components of Shatnez, were involved in history’s first murder, they remind us of how our relationship with other people is important. Therefore, it is fitting that the Mitzva of Shatnez be placed after the Mitzva of loving your fellow friend as you would love yourself.