Why Was Cain’s Offering Not Accepted?

In Genesis chapter 4 we find anger, jealousy, hatred, and finally murder. Cain killed Abel. Sin leads to more sin.

Genesis 4:1-5 Now the man had relations with his wife Eve, and she conceived and gave birth to Cain, and she said, “I have gotten a manchild with the help of the LORD.” Again, she gave birth to his brother Abel. And Abel was a keeper of flocks, but Cain was a tiller of the ground. So it came about in the course of time that Cain brought an offering to the LORD of the fruit of the ground. Abel, on his part also brought of the firstlings of his flock and of their fat portions. And the LORD had regard for Abel and for his offering; but for Cain and for his offering He had no regard. So Cain became very angry and his countenance fell. (NASB)

At this point many will say that God was not just because Cain was not a shepherd and therefore could not give a blood offering. But this line of thought has error because God did the same for Cain that he did for Abraham when he was about to offer Isaac as a sacrifice.

In Genesis 4:6-7 Then the LORD said to Cain, “Why are you angry? And why has your countenance  fallen?” If you do well, will not your countenance be lifted up? And if you do not do well, sin is crouching at the door; and its desire is for you, but you must master it.” (NASB)

God had provided Cain with an animal sacrifice right at his door. In Cain’s rebellion he chose to offer what he wanted rather than follow God’s plan. His sin was rebellion against God, and in that rebellion he murdered his brother Abel.