Mukhtasar Muslim (Abridged) 1025 — Sin of one who starts the practice

`Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with them) narrates that` the Messenger of Allah (peace and blessings be upon him) said: When any blood (murder) is shed unjustly, a portion of its burden (i.e., sin) falls upon the first son of Adam (Qabil), because he was the first to initiate the way of murder.