The First Murder 

After Allah accepted Habil’s sacrifice, Qabil realised that he had no chance of marrying his sister. This made him very angry, he threatened his brother, "I will kill you! I refuse to see you happy while I remain unhappy!".

One night, Habil was late returning home, so Adam (as) sent Qabil to find him. When he found him, he was still very angry at his brother Habil and said yours was accepted and mine was not”. Habil tried to guide his brother and said Allah only accepts from those who serve and fear Him, not from those who reject His commands”. This made Qabil even more angry, and he killed his brother by hitting him over his head. Qabil too fell in the trap of Iblees and then regretted immediately but it was too late. He did not know what to do with the body of his brother until he saw a crow digging a hole to bury another and then covering it. Qabil did exactly the same to hide the body of his brother.  

Adam (as) was very upset at the loss of both sons, one was murdered and other one was won over by Iblees. He prayed for his son and went on have many more children and grandchildren. He used to remind them all about Allah, and warn them about Iblees, their greatest enemy. He informed them of his own experiences with Iblees and how Iblees corrupted Qabil to murder his own brother.