The Prophet ﷺ said, "The first matter to be judged among people will be cases of bloodshed."
قال النبي ﷺ: أول ما يقضى الناس في الدماء.
Bukhari narrated it in the Book of Blood Money (6864) and Muslim in the Book of Qasama (1678), both through the route of Amash, from Abu Waail, from Ibn Masud, as mentioned.This does not contradict the hadith of Abu Hurairah, narrated as a saying of the Prophet, "The first thing for which a servant will be held accountable on the Day of Resurrection is his prescribed prayer. If it is sound, well and good, but if not, it will be supplemented from his voluntary prayers. Then the rest of the obligatory deeds will be dealt with in the same way."First, this hadith is mudtarib (inconsistently transmitted). Ibn Majah narrated it (1425) through the route of Ali bin Zayd, from Anas bin Hakeem Dabbi, who said, "Abu Hurairah said to me," and then mentioned it. Ahmad also narrated it (7902) through this same route, and it contains Ali bin Zayd, who is Ibn Jadan, and he is daif. Anas bin Hakeem Dabbi is also majhul (unknown).Tirmidhi (413) and Nasai (1/232) narrated it through the route of Hasan Basri, from Hurayth bin Qabisa, from Abu Hurairah, mentioning something similar, but Hurayth bin Qabisa is majhul.There is another route for it, narrated by Ahmad (9494), Abu Dawud (864), Hakim (1/262), and Bayhaqi (2/382), all through the route of Hasan, from Anas bin Hakeem Dabbi, from Abu Hurairah, as mentioned. This Hasan is the well known Imam Basri, who was a mudallis (one who conceals defects in transmission), and Anas bin Hakeem is majhul as previously noted.Daraqutni pointed out this discrepancy in his Ilal (8/247-249) and said, "The view closer to being correct is that of those who said, from Hasan, from Anas bin Hakeem, from Abu Hurairah."Second, even granting that this hadith is sahih, it should be understood as referring to the servant's worship of the Creator, while the hadith of Ibn Masud should be understood as referring to dealings between one servant and another.