Thus the blood of all the prophets would be required of them. Abel, of course, was the first martyr (Gen. 4:8; it is not clear why he should be called a prophet). Zechariah’s death was the last death of a prophet mentioned in the Old Testament, taking the books in their normal Hebrew order (2 Chr. 24:21f.). Jesus is saying that the blood of all those slain for their faithfulness to God will be required. It is laid at the door of this generation, because the people of the day fully share in the attitude that brought about the deaths of the prophets.
It isn’t that God likes meat rather than grain. The point is that he prefers a cheerful offering to a grudging one. A sacrifice is only pleasing to God if it comes with love.
Abel brings select portions of the first young animals from his flocks—and finds joy in doing so. Cain brings some grain, but his heart is hostile. He is the first person in the Bible to pretend religion—but it gives him no pleasure.
The pattern of sin and its consequences set in the garden is replayed throughout Genesis in the accounts of Cain, the generation of the flood, and the men of Sodom. The fall means that we humans are predisposed to sin. Though God punishes sin, sin does not thwart God’s ultimate, gracious purpose for His human creation. Embedded in the curse was the gleam of a promise that the offspring of the woman would someday lead the human race to triumph (3:15).
The consequences of sin became clear in the second generation when Cain, the oldest son, killed Abel his brother (4:8). Just as his parents had been expelled from the presence of God in the garden (3:23), so now Cain was expelled from human society to undertake a nomadic life in the east (4:16). Embedded in the curse was the gleam of grace, the “mark on Cain” (4:15), symbolizing God’s protection.