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." (Using translation from Bukhārī 3335)
قَالَ رَسُولُ اللهِ ﷺ «لَا تُقْتَلُ نَفْسٌ ظُلْمًا إِلَّا كَانَ عَلَى ابْنِ آدَمَ الْأَوَّلِ كِفْلٌ مِنْ دَمِهَا لِأَنَّهُ أَوَّلُ مَنْ سَنَّ الْقَتْلَ»