ייִדישער מחשבֿה אויף משלי 10:13

We find seven different interpretations in the Midrash concerning the nature of the "sign" that G-d made for Cain. The seven opinions reflect seven different considerations which may prevent man from sinning. Rabbi Yehudah describes the sign as an illumination of the sun's orbit at an unusual hour. The symbolism in this would be that Cain was taught that there are things in this world beyond tilling the soil. The "light" refers to "enlightenment." Rabbi Nechemyah, seeing that Cain at that time considered being a shepherd as the outer limit of enlightenment, felt that the light Rabbi Yehudah had talked about, would have been too advanced a message for Cain to have understood and to have an effect on him. He says, therefore, that the sign was a form of leprosy, to indicate that if acute suffering is the result of sinful behavior, such an experience would serve as a deterrent to sin in the future. We also find in the Torah that when a response to a sophisticated sign is not forthcoming, something more direct and down to earth is needed (compare Exodus chapter 3, when Moses questions whether the Israelites will accept him as their savior to be). Rabbi Abba says that Cain was given a dog, that just as the blind use the dog as a seeing eye, so Cain was given an external aid. This symbolizes man's dependence on guides which while inherently inferior to him, nonetheless assume leadership qualities for him if he does not live up to his potential. Abba Joseph says that Cain grew a horn on his forehead which would aid him in demolishing harmful philosophies, allegorically speaking. Rav says that this horn performs the function of frightening off would be murderers, i.e. the horn was to ward off physical rather than spiritual dangers. Rabbi Chanan says the horn was to serve notice that the owner was a repentant sinner. In either event, the meaning of the verse according to the last two sages would be that "G-d set Cain up as a sign," i.e. as a model for others to emulate. Rabbi Levi says that Cain's judgment was suspended pending further developments, until with the onset of the deluge this also included the penalty for the original murder. In the following verse we observe a partial rehabilitation of Cain, who founded civilization by building a city for his son Chanoch, thereby continuing the task that his murdered brother had originally set for himself.

Rabbi Yannai in the opening Midrash quoted, simply wanted to tell us that the lesson taught by the spice merchant had already been taught by Solomon in Proverbs.