Sahih al-Bukhari 6863
Sahih al-Bukhari · Book 87: Blood Money (Ad-Diyat) · “… And whoever kills a believer intentionally, his recompense is Hell …”
Narrated `Abdullah bin `Umar:
حَدَّثَنِي أَحْمَدُ بْنُ يَعْقُوبَ ، حَدَّثَنَا إِسْحَاقُ ، سَمِعْتُ أَبِي يُحَدِّثُ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ، قَالَ إِنَّ مِنْ وَرْطَاتِ الأُمُورِ الَّتِي لاَ مَخْرَجَ لِمَنْ أَوْقَعَ نَفْسَهُ فِيهَا، سَفْكَ الدَّمِ الْحَرَامِ بِغَيْرِ حِلِّهِ.
One of the evil deeds with bad consequence from which there is no escape for the one who is involved in it is to kill someone unlawfully.