One Murder is Equal to the Killing the Whole of Humanity
“Whoever slays a soul, unless it be for a manslaughter or for mischief in the land, it is as though he slew all men; and whoever keeps it alive, it is as though he kept alive all men.”
(Surah al-MÄ’ida 5:32)
All the believers are sons of Adam (a.s.) and brothers to one another. One who kills another person perpetrates a great evil and instigates a feeling of malice, revenge and hatred among people.