Informed Comment

CAIN. Arabic قابل Qabil.
The account of Cain and Abel is given in the Qur’an, Surah v. 30, will be found in the article ABEL. The Commentators say that the occasion of making the offering was as follows: Each of them being born with a twin sister, Adam by God’s direction ordered Cain to marry Abel’s twin sister, and Abel to marry Cain’s, but that Cain refused. They were then ordered to submit the question by making a sacrifice, and Cain offered a sheaf of the very worst of his corn, whilst Abel offered the best fatted lamb of his flock. (Tafsiru ‘l-Baizawi, in loco.)

Based on Hughes, Dictionary of Islam