Three sacrifices are presented in the story of Cain and Able following the fall of Adam and Evil. After banishment from the Garden of Eden, sacrifice is the first interaction of man with the Lord.
Both Cain and Able offer sacrifices. The Lord is pleased with Able’s, but not with Cain’s. A close reading of the text is needed to understand why. In the course of time Cain brought to the LORD an offering of the fruit of the ground, and Abel brought of the firstlings of his flock and of their fat portions. Cain brought “an offering,” while Able brought “fat portions” of his “firstlings.” Cain brought just an offering, neither the first nor the best he had to offer, while Able brought his first and best.
From this we see that God desires the best we have. Not because he needs what we have to offer. Rather, he desires the best we have to offer to teach us how to give as he gives and to love as he loves.
Cain is resentful of God’s regard for his brother’s offering over his and slays Able. Able’s blood is poured out upon the land and cries out to Lord. In this regard, the pouring of the life force – blood – of Able upon the land is seen as a sacrificial offering.
The Church Fathers saw the food offerings of Cain and Able as prototypes of the bloody and non-bloody food offerings of Old Testament. They also saw the lamb that Able offered as a prototype of the crucifixion of Lamb of God, the only Son of the Lord and best he had to offer, and accordingly as a prototype of the Holy Eucharist.