1 The man had relations with his wife Eve, and she conceived and bore Cain, saying, “I have produced a man with the help of the LORD.” 2 Next she bore his brother Abel. Abel became a keeper of flocks, and Cain a tiller of the soil. 3 In the course of time Cain brought an offering to the LORD from the fruit of the soil, 4 while Abel, for his part, brought one of the best firstlings of his flock. The LORD looked with favor on Abel and his offering, 5 but on Cain and his offering he did not. Cain greatly resented this and was crestfallen. 6 So the LORD said to Cain: “Why are you so resentful and crestfallen? 7 If you do well, you can hold up your head; but if not, sin is a demon lurking at the door: his urge is toward you, yet you can be his master.” 8 Cain said to his brother Abel, “Let us go out in the field.” When they were in the field, Cain attacked his brother Abel and killed him. 9 Then the LORD asked Cain, “Where is your brother Abel?” He answered, “I do not know. Am I my brother’s keeper?” 10 The LORD then said: "What have you done! Listen: your brother’s blood cries out to me from the soil!
I do not usually quote such large portions of the Bible, but I feel it is necessary to explain this very complicated yet simple concept. Why was Cain’s sacrifice not looked upon with favor by God? After all he worked hard to bring forth the fruits of his labor, and all Abel did was watch over some sheep. Abel brought forth the “firstling” and God looked upon it with favor. This mystery is explained by the crucifixion of Christ. God offered up his first born as a sacrifice for our salvation, and Cain offered up the work of his hands. While important, the work of our hands is not sufficient for our salvation. We need Jesus, the sacrifice of the lamb. This is what God is telling us in this scripture.
I always wondered why Cain killed Abel. It became evident to me through the Church. Just as Abel offered the sacrifice of the innocent so did God offer his Son. Those who offer the sacrifice of their hands only, are envious of the Church, they are of the world. Therefore, God reveals though scripture the martyrs of the Church. Just as Cain slaughtered Abel so have our saints been slaughtered, and their blood cries out to the heavens.