Genesis 4 Matthew 4 Ezra 4 Acts 4

In Genesis 4, we're face to face with some of the darkest instincts of human beings. The two sons of Adam and Eve offer sacrifices; Abel's animal sacrifices are accepted, but Cain's grain offerings aren't. There's no indication as to why: that's just how it is. But Cain's reaction is anger – and God's words to him offer a profound insight into the nature of temptation. He challenges Cain to 'do what is right'. Sin is pictured as 'crouching at the door' (verse 7, ESV); it's like a wild animal that must be tamed or it will destroy him. Instead, sin masters Cain.

The picture here is of human nature as a battleground, with sin as the enemy. When we give way to anger, resentment or pride we are opening the door to evil, and evil is stronger than we think. We might think we can master these instincts, but when we give them room in our hearts we have already failed.

Cain's question, 'Am I my brother's keeper?' is meant rhetorically, assuming the answer is 'No'. In fact, we are all responsible for each other; overwhelmed by sin, Cain fails to see this. 

God tells Cain that Abel's blood is 'crying out to me from the ground' (verse 10). It is crying out for vengeance, and Cain is banished. But Hebrews 12.24 speaks of the 'sprinkled blood' of Christ, that 'speaks a better word than the blood of Abel'. Abel's blood cries out for vengeance; Christ's blood cries out for mercy and forgiveness.