“… And whoever kills a believer intentionally, his recompense is Hell …” Sahih al-Bukhari 6862

Arabic hadith text
حَدَّثَنَا عَلِيٌّ، حَدَّثَنَا إِسْحَاقُ بْنُ سَعِيدِ بْنِ عَمْرِو بْنِ سَعِيدِ بْنِ الْعَاصِ، عَنْ أَبِيهِ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏لَنْ يَزَالَ الْمُؤْمِنُ فِي فُسْحَةٍ مِنْ دِينِهِ، مَا لَمْ يُصِبْ دَمًا حَرَامًا ‏"
Translation
Narrated Ibn `Umar

Allah's Messenger (ﷺ) said, "A faithful believer remains at liberty regarding his religion unless he kills somebody unlawfully."