It is told by some of the companions that Adam used to wed the son from one birth to the daughter from another birth. From each pregnancy was one male and one female, no birth siblings were to marry each other. Abel (Habil) wanted to wed the sister of Cain (Qabil). Cain was older than Abel and his sister was more beautiful, so Cain wanted to keep her for himself. His father, Adam told Cain to marry off his sister to Abel but he refused. Adam told them to do a sacrifice and then left to perform Hajj, which they did. Abel sacrificed a big lamb as he was a shepard and Cain a bundle of the worst crops he had grown.

Later, a fire came down and engulfed the sacrifice of Abel but not that of Cain. Cain became angry, threatening to kill him so that he could not marry his sister. He replied as below.

Relate to them in truth ˹O Prophet˺ the story of Adam’s two sons—how each offered a sacrifice: one’s offering was accepted while the other’s was not, so he threatened ˹his brother˺, “I will kill you!” His brother replied, “Allah only accepts ˹the offering˺ of the sincerely devout.5:27

If you raise your hand to kill me, I will not raise mine to kill you, because I fear Allah—the Lord of all worlds.5:28

I want to let you bear your sin against me along with your other sins, then you will be one of those destined to the Fire. And that is the reward of the wrongdoers.”5:29

In Abdullah bin Amr's version it is narrated that Abel was stronger than Cain but his obedience to Allah stopped him from sinning. Ja'far Al-Baqir said as Adam was watching Abel's sacrifice being accepted, Cain said to him that the only reason Abel's sacrifice was accepted was because Adam prayed for him. Ja'far said that one day Abel was out looking after his flock but did not come back, so Adam told Cain to look for him. This is when he began to complain about his sacrifice not being accepted and Abel explained only sincere sacrifices are accepted. Then was killed by hitting iron he had in his hand when Cain became frustrated. Others say the impact was from a rock hit onto his head whilst sleeping, or that he was strangled to death and bitten by Cain. Allah knows best. Regardless, the response of Abel is one of noble character and piety.

Still, the other convinced himself to kill his own brother, so he killed him—becoming a loser.5:30

Then Allah sent a crow digging ˹a grave˺ in the ground ˹for a dead crow˺, in order to show him how to bury the corpse of his brother. He cried, “Alas! Have I ˹even˺ failed to be like this crow and bury the corpse of my brother?” So he became regretful. 5:31

Cain did not know what to do with Abel's corpse, he wandered around aimlessly trying to figure out where to hide it. He began to feel guilt about what he did. Two ravens were sent out of mercy to show Cain how to bury a corpse. They began fighting until one died and the other buried him. Cain exclaimed as above and then proceeded to bury his brother. This was the first burial of humankind.

Allah's Messenger ﷺ said, "Whenever a person is murdered unjustly, there is a share from the burden of the crime on the first son of Adam for he was the first to start the tradition of murdering." [Bukhari 3335, Muslim 1677, Ahmad 1/383] He also said "There is no sin more worthy of Allah hastening the punishment upon its practitioner in the world – along with what is in store for him in the Hereafter – than tyranny and severing the ties of kinship.” [At-Tirmidhi 2511]

Ibn Kathir highlights that in the Torah we find that Allah postponed the punishment of Cain, he lived in a place called Nawad in the east of Aden (in Yemen), now named Qinin. He had a son called Enoch (Idris), who had a son called Irad, who had a son called Mehujael, who had a son called Methushael, who had a son called Lamech. Their lineage continued. In our tradition, Imam Abu Ja'far bin Jarir says that Eve had 40 pregnancies, some say 120 - each having one male and one female. The eldest was Cain and Qalima (his sister), the youngest being Abdul-mughith and Umm-ul-Mughith.

He is the One Who created you from a single soul, then from it made its spouse so he may find comfort in her. After he had been united with her, she carried a light burden that developed gradually. When it grew heavy, they prayed to Allah, their Lord, “If you grant us good offspring, we will certainly be grateful.”7:189

But when He granted their descendants good offspring, they associated false gods in what He has given them. Exalted is Allah above what they associate ˹with Him˺!7:190

We are told that Abu Dhar said "O Messenger of Allah! How many prophets were there? He replied 'one hundred and twenty four thousand.' I said 'O Messenger of Allah! How many of them were messengers?' He replied 'Three hundred and thirteen: quite a big number.' I said 'O Messenger of Allah! Who was the first of them?' He said 'Adam.' I said 'O Messenger of Allah! Was he a prophet and a messenger? He said 'Yes, Allah created him with His Hand, then He breathed into him the soul which He created for him, then He gave him a perfect shape'." [Ibn Hibban 361]

Elsewhere we are told in the miraculous night journey that “When the Prophet [ﷺ] passed by Adam on the first heaven, he said: "Welcome to the pious son and pious Prophet." The Prophet [ﷺ] then said: "On his right side was a huge crowd, and on his left side was a huge crowd. When he looked on his right side, he smiled; and when he looked on his left side, he cried. I (the Prophet [ﷺ]) said: 'O Gabriel! Who is this?' He replied: 'He is Adam. and they are the souls of his children. When he looked on his right, to those who were the people of Paradise, he smiled; but when he looked on his left, to those who were the people of Hell, he cried."" [Bukhari 349, 3342, Muslim 163]