فَطَوَّعَتۡ لَهُۥ نَفۡسُهُۥ قَتۡلَ أَخِيهِ فَقَتَلَهُۥ فَأَصۡبَحَ مِنَ ٱلۡخَٰسِرِينَ ٣٠
And his soul permitted to him1 the murder of his brother, so he killed him and became among the losers.
Translation: Saheeh International (English)
1 i.e., the killer allowed himself.
Each word's meaning and sound
The evil prompting soul of Cain persuaded him to wrongly kill his brother, Abel. So he killed him and because of that he became one of those who are losers in this world and the Afterlife. He set a bad example and will therefore bear that burden, as well as the burden of any person who does the same until the Day of Judgement, without any reduction in the burden of those who imitate him.
Al-Mukhtasar in interpreting the Noble Quran