The first murder on the earth 

  Allah Almighty says in Ayat (27-31) of Surat Alma'idah "And Recite to them the news of the two sons of Adam, in truth, when they both offered a sacrifice, and it was accepted from one of them but it was not accepted from the other, he said I will surely kill you, he said indeed, Allah only accepts from the righteous, if you should extend your hand against me to kill me, I shall not extend my hand against you to kill you, indeed, I fear Allah, the Lord of the worlds, indeed, I want you to bear my sin and your sin, so you will be among the companions of the Fire, and that is the recompense of the wrongdoers, and his soul permitted to him the murder of his brother, so he killed him and became among the losers, then Allah sent a crow searching in the ground to show him how to hide the body of his brother, he said O woe to me! Have I been unable to be like this crow and hide the body of my brother?, and he became of the regretful".

 Allah commanded His Messenger Muhammad to recite to His people the news of Cain (Qabil) and Abel (Habil), the two sons of Adam in truth, when they both offered a sacrifice to Allah, and Allah accepted the sacrifice from one of them, and did not accept from the other, and it was said that Allah has prescribed for Adam to marry His daughters to His sons due to the necessity as there were no children on the earth except from the lineage of Adam, so in every time twins, a male and a female, were born to Adam, so He would marry the female of one twin to the male of the other twin, and Abel's sister was ugly, while Cain's sister was beautiful, so Cain wanted to keep his sister for himself, but Adam refused to do so unless they both offer an offering, and whoever Allah accepts his offering, then she is his, so they both offered an offering, and it was accepted from Abel, and Allah has sent a fire to consume Abel's offering, but it was not accepted from Cain, thereupon, Cain said to his brother Abel out of envy and enmity towards him I will surely kill you, then Abel said to him indeed, Allah only accepts from the righteous who fear Allah and fear His punishment, so they act according to His commands and prohibitions, then He said to Cain if you should extend your hand against me to kill me, I shall not extend my hand against you to kill you so I will not reciprocate your evil deeds with the same, so then we would be equal in sin, indeed, I fear Allah, the Lord of the worlds, and I fear His punishment if I do what He has not permitted.

 Then Abel said to his brother Cain I want you to bear the sin of killing me and the sin that you have committed before, so you will be among the companions of the Fire on the day of resurrection, and that is the recompense of the wrongdoers who transgress Allah's commands and turn away from the path of guidance, undoubtedly, Cain will bear the sin of every human being who was killed without right until the day of resurrection, where as narrated by Abdullah bin Mas'ud that Allah's Messenger (PBUH) said: "Whenever a soul is murdered unjustly but there is a share of the burden of its blood on the first son of Adam for he was the first to introduce murdering" (Sahih Albukhari 3335).

 The soul of Cain permitted to him the murder of his brother Abel, so his soul made the matter easier for him and encouraged him to kill his brother, then he became among the losers in the worldly life and the Hereafter, so the murdered brother earned forgiveness for his sins and was admitted to Paradise, while the murderer failed and lost himself in the worldly life and the Hereafter, after Cain killed Abel, he did not know how to deal with the corpse of Abel, then Allah taught him how to bury his brother by sending a living crow searching in the ground in order to bury a dead crow, then Cain said O woe to me! Have I been unable to be like this crow and hide the body of my brother?, and he became of the regretful for what he had committed of disobedience to Allah and for killing his brother.