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] (ID)
App reference (ID): Book 19, Hadith 38 (ID)
Arabic/English book reference (ID): Book 19, Hadith 1845 (ID)