What could Cain have been thinking? Why kill Abel? Detectives look for motives and usually trace them to money or sex. The record shows that neither played a role in the first murder.
Both Cain and Abel brought offerings to God. God respected Abel’s offering but not Cain’s. Cain was upset and depressed over this and God said, “Why are you angry and why is your countenance [face] fallen? If thou doest well, shall it not be lifted up?” (Gen 4:6-7). From this we can infer at least two things: first, Cain had a great desire for God’s approval and second, God had told Cain and Abel what to do. Even a human father would not tell his son, “If you do right, I will reward you,” unless the son had been told what the right way was! Thus, Abel offered in the way God describes as “doing well,” but Cain offered in another way and was rejected.
Though he was unwilling to do things God’s way, Cain still wanted God’s approval. As there were only two of that generation in the world, it must have appeared to Cain that if Abel were taken out of the picture, God would have no other choice but to accept him. Besides, no man likes to be upstaged by his little brother. In his wrath over being rejected and in his desire to be approved by God, Cain slew Abel. It seems so tragic--how much simpler to just do things God’s way and live in peace.
Following God’s rules is called “walking by faith” (2 Cor 5:7; Heb 11). Today, many people still seek to gain God’s approval without the sacrifices involved in walking God’s narrow way. They look just fine to themselves and to each other; they may even congratulate themselves on being “better than average.” They are religious and sincere. What more could anyone ask? Usually, they are even admired by the “average” folks.
Then appears a righteous man who obeys God’s word exactly from a sincere heart. As a result, like Cain’s, others’ offerings are exposed as inadequate. If Abel could do it right, Cain could have also. If a man can live “holily and righteously,” walking by faith in all the ways of God, then so could these “religious” men. All too often they go the way of Cain and kill the righteous – by slander, by persecutions, by mockery, by ostracism. Why not repent and follow the example of the “Abel?” Because “their works are evil;” they are set in their hearts to do things their own way. The Cains see the Abels as an accusation against their religion, label them “narrow,” “bigoted,” “judgmental,” “legalistic,” and thus they seek to justify themselves.
Researching Bible history appears to establish that everyone is a Cain or an Abel. Not everyone actually murders an Abel, some “just” applaud, or stand by indifferently. Insofar as meeting God’s standard is concerned, being an Abel is not so difficult, but it takes much courage—there are a lot of Cains in the world….and many that are innocently called, “brother.”
By faith Abel offered to God a more acceptable sacrifice than Cain, through which he was commended as righteous, God commending him by accepting his gifts. And through his faith, though he died, he still speaks. Hebrews 11:4