Messenger of Allah 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."  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تُقْتَلُ نَفْسٌ ظُلْمًا إِلاَّ كَانَ عَلَى ابْنِ آدَمَ الأَوَّلِ كِفْلٌ مِنْ دَمِهَا لأَنَّهُ أَوَّلُ مَنْ سَنَّ الْقَتْلَ