Two brothers
“If you do well, won’t it be lifted up? If you don’t do well, sin crouches at the door. Its desire is for you, but you are to rule over it.””Genesis 4:7 · WEB
One generation after the garden, the damage reaches the family. Two brothers bring offerings; one is received and one is not, and the text refuses to explain why in the detail we would like. What it does record is God speaking to the angry brother before anything happens — a warning and an invitation in one breath: sin is crouching at your door, and you can master it. Cain hears it and goes out to the field anyway. Afterwards comes the question that every human being has since learned to ask defensively: "Am I my brother's keeper?" The Bible's whole answer is yes. Even then, the God who marks Cain marks him for protection, not for destruction. The story is honest about how quickly envy becomes violence, and how early God stood in the way of it.