The Messenger of Allah ﷺ said, "The first matter to be judged between people on the Day of Resurrection will be matters of bloodshed."
أخبرنا أحمد بن حرب قال حدثنا أبو معاوية عن الأعمش عن أبي وائل
قال رسول الله ﷺ أول ما يقضى فيه بين الناس يوم القيامة في الدماء
[Sahih], and it is in Kubra, hadith no. 3458. It is mursal, and it has many corroborating narrations, some of which have already been mentioned.