“The Lord saw how great the wickedness of 
human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time.”
Genesis 6:5 NIV
http://bible.com/111/gen.6.5.niv
From Genesis 4:1-16
Adam and Eve wanted to impart to their sons the wisdom and the teachings they had learned from the LORD GOD in the garden. They knew this was what the LORD wanted them to do. It became harder and harder for them to recall everything they had learned at his feet, but they taught what they knew. They taught them through words and deeds the command God gave to them to fill the earth, and subdue it. To use all its vast resources and serve God and their fellow man. Be responsible for all living things that move on the face of the earth. Adam and Eve spoke freely of their time in the garden of Eden to Cain and Abel. They told them about the Creator LORD GOD. As time passed Cain became a tiller of the ground. He worked the earth. He found his identity in being a farmer. He sought to acquire ground and all the earth had to possess. Cain had a special relationship with the ground. It gave him roots. The ground gave him a place to be and a place to call his own. The ground provided for him. At the opposite end of the spectrum, Abel was a herdsman. Abel was a shepherd. Whereas Cain heard the call of the earth, Abel heard the call of a caretaker. His nature was to nurture. His nature was to give and not take. Eve pondered the difference in her two sons. The one who was out to acquire all he could possess and the other to give of what he had been given. Two very different boys with very different perspectives of life who came from the same womb. Some days as she observed Cain she caught a fleeting glimpse of the seed of discontent beginning to take root in his soul. She would catch a stab of jealously in him. She recognized this seed for it was the same one that grew in her so long ago in the garden. And yet she didn’t know what to do. She chose to ignore it instead, hoping it would all go well. She did not remember to call on the LORD for help. That wisdom was hidden from her now because she had chosen her own way and not the LORD’S.
Time passed and Cain decided to bring an offering to GOD. He brought some produce from his farm. Abel decided to do the same. He brought the firstborn of his flock. He brought GOD his best. He brought the LORD GOD the choice cuts of meat. GOD accepted Abel’s offering. He knew Abel offered HIM his best he could bring. GOD saw into Abel’s heart. He saw that Abel’s offering was prompted by faith. He didn’t
approve of Cain and his offering. He could see into Cain’s heart. GOD sees what man cannot see. He could see sin waiting to pounce and spring up in Cain. LORD GOD already knew of the seed of jealousy lying dormant in Cain’s soul just waiting to be watered. GOD knew beforehand the outburst Cain was about to unleash.
“Your being unfair. Why was my brother’s offering acceptable and mine was not,” Cain shouted at GOD. “There were so many voices sounding off in his ears where we they coming from,” Cain thought to himself. He heard every lie whispered to him and he believed every last one of them. “GOD doesn’t love you, if HE did HE would have accepted your offering. GOD doesn’t think you are good enough.” All these whisperings, they drove him crazy and he flew into a temper tantrum. He became depressed because he bought into the lies. He became downcast because he was dejected. He couldn’t look into his own heart and see the truth. He didn’t offer GOD his best. His offering was all show and no heart, but he couldn’t see this truth. He didn’t want to see it. “Come Cain,” GOD tried to lead him. “Come let us reason together. If you do well, will you not be accepted? But if you do not do well, sin crouches at your door. Sin desires to overtake you, but you must master it.” They watched over the two brothers as Cain and Abel left that place. The Father, the Son, and the Holy Spirit. They knew the good or the evil that Cain must choose from, and they knew the outcome. The choice must always lay with man. They created inside of a man a place where choices must be made. It is from that place of choice where mankind chooses to love God in return. The Trinity would never override that place. So they watched the two brothers walk away.
Cain put his arm around Abel as he led Abel to a field. Rage was boiling inside of him like a volcano about to erupt. He could barely contain himself until he thought they were out of earshot of the LORD GOD. He squeezed the back of Abel’s neck as they walked along. “Ow your hurting me Cain,” Abel told him. “What is wrong with you? You are acting like one of my sheep all caged up.” Finally, Cain could not hold back. He unleashed his wrath. “What is wrong with me? What is wrong with me?” he screamed, “What is wrong with you little brother? How could you do that to me in front of GOD?” “Do what?” Abel wondered. “What did I do?” “You know exactly what you did. You stood me up. You made yourself look so superior to me. You brought your firstborn and your choicest meat,” Cain words spewed out of him. He could no longer contain all the pent up jealousy he had harbored all these years with Abel. “It was my idea in the first place to bring an offering to the LORD. And then here you come, horning in on my idea. And you decide to bring your best. You knew exactly what you were doing. You were out to make me look foolish,” Cain unleashed on Abel. The more he screamed the more out of control he became. He was beyond the point of reason now. Abel was scared. He turned to run, but Cain pounced. He knocked Abel to the ground. Cain was trembling with rage, and rage and anger were now his masters. He gave into the anarchy flowing through his thoughts. He doubled up his fist and hit Abel in the nose. He broke it. Blood flowed out and onto the ground. Abel tried to free himself. He struggled beneath his brother, but it seemed once Cain saw the blood flowing from his nose he wanted more. Abel knew at that point this would not end until all his blood flowed to the ground. Cain kept pounding on Abel’s face. Abel lost consciousness. He couldn’t fight back. And still Cain pounded away. He gave into the anarchy that threatened to overtake him. Cain saw a sharp boulder near by. The ground had provided his last weapon. He picked it up and dropped it on Abel’s skull and watched his blood flow onto the ground. Cain looked at his hands they were bloody raw. His brother’s blood covered them. He tried wiping them on his clothing. He then realized he had given over to the voices in his head. He had joined the evil one. Sin had mastered him. Because jealousy and envy controlled Cain, he did an exceedingly vile act. He committed the first murder of mankind. He then heard the LORD’S question. “Where is Abel your brother?” For the second time the LORD GOD asked man the rhetorical “where”. He once asked Adam, “Where are you?” HE knew the answer. He wanted man to make a realization of sin. But Cain was to indebted to the dark side he would not play this game with the LORD. “How should I know. Am I my brother’s keeper?” He said to the LORD with sarcasm dripping from his voice. Cain thought he would hide his actions behind disrespect. He knew his parents teaching to be responsible for all living things and to serve his fellow man, but he pretended ignorance in the face of God’s question. “What have you done, Cain?” God asked him. Sorrow and anger was dripping from HIS words. “The voice of your brother’s blood is crying to me from the ground you seem to worship.” The LORD GOD had put life in the blood of man, and now that life was calling out to HIM. And for the second time the LORD GOD was forced to issue a curse and a punishment onto man. Once again, GOD issued a curse upon the ground, “This same ground your brother died on will now be cursed to you. It will no longer yield to you produce. You will not gain strength nor sustenance from it. You will farm it but it will not give you its best. You will be a vagabond and a fugitive on the earth. You will be in perpetual exile, always an outcast living on this earth.” God’s curse took away Cain’s identity. He lost his roots. He had no place to be or to call his own. God’s words sent him into a free fall. He felt like his world was spinning out of control. “My punishment is greater than I can bear,” he cried to the LORD. “You have driven me out from the face of the land. I can’t take it. I can never see Your face again. I have no home. I am a wanderer on Earth. Whoever finds me will kill me,” Cain had lost all hope in that moment. He had lost hope because he still would not admit his guilt. His lack of repentance led to his feeling of hopelessness. He had been driven away from the ground, his roots. He no longer had identity. God’s holiness could not be ignored, but His mercy could not be ignored either. So in mercy God spoke, “If anyone kills Cain, vengeance shall be taken on him sevenfold.” And the LORD set a mark or sign upon Cain, lest anyone finding him should kill him. The LORD GOD is just and good and merciful all in one. Just as He restored Adam and Eve after their sin, with this one act He restored Cain after his sin. For nothing is too hard for God. Part of His nature is to redeem the fallen. He wanted to show mankind nothing is too great, too far out of His reach that He cannot redeem. So Cain went away fro the presence of the Lord and lives in the land of wandering, east of Eden.
With a single act of violence, Adam and Eve lost both sons in a day. When they heard the news, they were driven to their knees. They felt all joy leave them. Their hearts broke simultaneously. Their lives were not created for this type of loss. A parent should never have to outlive their child. They knew they would never have experienced such vile acts in the garden before their Choice. Regret once again flooded their beings.