( 27 ) And recite to them the story of Adam's two sons, in truth, when they both offered a sacrifice [to Allah], and it was accepted from one of them but was not accepted from the other. Said [the latter], "I will surely kill you." Said [the former], "Indeed, Allah only accepts from the righteous [who fear Him].
( 28 ) If you should raise your hand against me to kill me - I shall not raise my hand against you to kill you. Indeed, I fear Allah, Lord of the worlds.
( 29 ) Indeed I want you to obtain [thereby] my sin and your sin so you will be among the companions of the Fire. And that is the recompense of wrongdoers."
( 30 ) And his soul permitted to him the murder of his brother, so he killed him and became among the losers.
( 31 ) Then Allah sent a crow searching in the ground to show him how to hide the disgrace of his brother. He said, "O woe to me! Have I failed to be like this crow and hide the body of my brother?" And he became of the regretful.
Cain was jealous of his brother. Able had brought Jesus the lamb (which was the sacrifice) and Cain brought Jesus fruit. (which he did not ask for) so Jesus marked cain! so Cain killed Able out of jealousy!
While some point out that Cain’s offering is not said to be of the choicest fruits whereas Abel’s offering is specified to have been of the “firstlings of his flock, even their fatty pieces,” the problem was not in the quality of produce that Cain offered. As Hebrews 11:4 points out, Cain’s offering lacked the motivation of faith that made Abel’s sacrifice acceptable. The fact that God did not view Cain’s offering with favor may also have been because his offering was bloodless, whereas Abel’s represented a life poured out.
The manner in which the distinction between the approved and the disapproved offerings was made is not stated, but it was undoubtedly evident to both Cain and Abel. Jehovah, who reads the heart of man (1Sa 16:7; Ps 139:1-6), knew the wrong attitude of Cain, and His rejection of Cain’s sacrifice resulted in that wrong disposition being made clearly manifest.
“The works of the flesh” now began to be openly produced by Cain: “enmities, strife, jealousy, fits of anger” resulting in his murdering his brother. (Ga 5:19, 20)
The Cain-Abel story is an allegory for the transition of human society from hunter-gatherers (represented by Abel) to farmers (represented by Cain), and the triumph of the latter. It has parallels in Sumerian stories, and is probably rooted in the beginnings of human society. It is a mistake to think of it as a literal history of two individuals.
Both Cain and Abel gave offerings to God. Abel gave God his best meat from his sheep and did so with much respect and love. But Cain gave his offering, not as lovingly as Abel. God was pleased with Abel’s offering of a lamb, but not with Cain’s offering from his harvest. Cain was jealous so in a fit of anger he killed his brother. It was jealousy.
We must not be like Cain, who belonged to the evil one and killed his brother. And why did he kill him? Because Cain had been doing what was evil, and his brother had been doing what was righteous. (1 John 3:12 NLT)