مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4185
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah said: The Messenger of Allah (ﷺ) said: “The first matter concerning which judgement will be passed among the people on the Day of Resurrection is bloodshed.”
Musnad Ahmad 4213Its isnad is saheeh, Muslim (1678)]