Ibn Mas'ud (May Allah be pleased with him) reported:
The Prophet ﷺ said, "The first matter concerning which people will be judged on the Day of Resurrection will be the matter of blood."

[Al-Bukhari and Muslim].

وعن ابن مسعود رضي الله عنه قال: قال النبي ﷺ : "أول ما يقضى بين الناس يوم القيامة في الدماء" ((متفق عليه)).