If you do well, will you not be accepted? And if you do not do well, sin is crouching at the door. Its desire is for you, but you must rule over it. Genesis 4:7
In betraying God’s word, Adam and Eve were displaced from Eden and from their perfect union with God. The Lord did not remove himself completely from their lives and He continued to communicate with them, and their family, guiding them in His will.
Cain and Abel would both have grown up in the knowledge of what happened in the garden. They would understand what was acceptable, what was unacceptable and what the consequences were of disregarding God’s will.
Abel clearly understood what was required of him in honouring the LORD; blood must be shed in order to be right with God. For this reason, Abel ‘brought of the firstborn of his flock.’ This was an acceptable sacrifice in the eyes of God. Cain knew the same truths as Abel and yet he decided not to include a blood sacrifice with his offering. He did not do well before God; he did not bring the correct offering and the Lord had no regard for it.
Cain was so angry, feeling that his hard work and labour were not good enough for God. The bible is very clear though, from Genesis to Revelation, you cannot work your way into righteousness, no matter how hard you try. Abel and Cain were both sinners before God; their offering was the only difference between them. Abel had faith in the blood that was shed, through which he was made righteous before God.
Sin desires to have every one of us. It is crouching at the door waiting for us to disregard God’s will and His governance, but we have the power to rule over it.
For us, Jesus is the only acceptable offering, for by his blood we are cleansed from all sin and from all unrighteousness.