Originally Posted by Contra_Mundum

I am convinced that Cain's sacrifice was unacceptable on account of his heart, which led him to proffer that which was unacceptable in form. In other words, his offering was entirely unacceptable, the will-worship of his offering being an index of his rebellious heart.

So my slight disagreement with Vic would be that I don't see Cain as being slipshod in his choice, but rather refusing to trade his own sweated labors for a sheep of Abel's flock. I doubt it was the best of his field either, but after he rejects God's exemplary means I don't even think it mattered if the fruit was hi-quality or not.

Cain said, in essence, "God ought to accept from the labor of my hands that which I deem worthwhile." The contrasts with Abel's offerings are more than superficial. Beside being an atoning sacrifice, Abel's is "of the fat" or best; nothing at all is said about the quality or first-fruit of Cain's, which was not bloody (a requirement that is simply fundamental). Even assuming God was in the habit of receiving "peace" offerings of grain at this time (and there is no indicator that he had authorized them), Cain is clearly not at peace with God, for his "offering" is rejected.