Musnad Abu Ya'la al-Mawsili 152:147

Abu Khaythama narrated to us, Waki' narrated to us, al-A'mash narrated to us, from Abu Wa'il, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The first thing that will be judged between the people on the Day of Resurrection is [regarding] the blood."