After Allah mentioned the ruling of unintentional murder, He mentioned the ruling for intentional murder. Allah said,

﴿وَمَن يَقْتُلْ مُؤْمِناً مُّتَعَمِّداً﴾

(And whoever kills a believer intentionally,) This Ayah carries a stern warning and promise for those who commit so grave a sin that it is mentioned along with Shirk in several Ayat of Allah's Book. For instance, in Surat Al-Furqan, Allah said,

﴿وَالَّذِينَ لاَ يَدْعُونَ مَعَ اللَّهِ إِلَـهَا ءَاخَرَ وَلاَ يَقْتُلُونَ النَّفْسَ الَّتِى حَرَّمَ اللَّهُ إِلاَّ بِالْحَقِّ﴾

(And those who invoke not any other god along with Allah, nor kill such person as Allah has forbidden, except for just cause). Allah said,

﴿قُلْ تَعَالَوْاْ أَتْلُ مَا حَرَّمَ رَبُّكُمْ عَلَيْكُمْ أَلاَّ تُشْرِكُواْ بِهِ شَيْئاً﴾

(Say: "Come, I will recite what your Lord has prohibited you from: Join not anything in worship with Him.) ﴿6:151﴾. There are many Ayat and Hadiths that prohibit murder. In the Two Sahihs, it is recorded that Ibn Mas`ud said that the Messenger of Allah said,

«أَوَّلُ مَا يُقْضَى بَيْنَ النَّاسِ يَوْمَ الْقِيَامَةِ فِي الدِّمَاء»

(Blood offenses are the first disputes to be judged between the people on the Day of Resurrection. ) In a Hadith that Abu Dawud recorded, `Ubadah bin As-Samit states that the Messenger of Allah said,

«لَا يَزَالُ الْمُؤْمِنُ مُعْنِقًا صَالِحًا، مَا لَمْ يُصِبْ دَمًا حَرَامًا، فَإِذَا أَصَابَ دَمًا حَرَامًا بَلَّح»

(The believer will remain unburdened in righteousness as long as he does not shed prohibited blood. When he sheds forbidden blood, he will become burdened.) Another Hadith, states,

«لَزَوَالُ الدُّنْيَا أَهْوَنُ عِنْدَ اللهِ مِنْ قَتْلِ رَجُلٍ مُسْلِم»

(The destruction of this earthly life is less significant before Allah than killing a Muslim man (or woman).)