“… And whoever kills a believer intentionally, his recompense is Hell …” Sahih al-Bukhari 6864

Arabic hadith text
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى، عَنِ الأَعْمَشِ، عَنْ أَبِي وَائِلٍ، عَنْ عَبْدِ اللَّهِ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏أَوَّلُ مَا يُقْضَى بَيْنَ النَّاسِ فِي الدِّمَاءِ ‏"
Translation
Narrated `Abdullah

The Prophet (ﷺ) said, "The first cases to be decided among the people (on the Day of Resurrection) will be those of blood-shed."