The Messenger of Allah ﷺ said, "The first matter to be judged between people on the Day of Judgment will concern the shedding of blood."
حدثنا محمود بن غيلان حدثنا وهب بن جرير حدثنا شعبة عن الأعمش عن أبي وائل
قال رسول الله ﷺ إن أول ما يحكم بين العباد في الدماء
Sourced. Agreed upon [by Bukhari and Muslim]. Also in Muslim, Qasamah and Muharibin, chapter on requital for bloodshed in the hereafter, etc., no. 1678, from the hadith of Shubah. Bukhari, no. 6533, from the hadith of Amash, similarly.