"I heard Kharijah bin Zaid bin Thabit narrate that his father said: (The Verse) 'And whoever kills a believer intentionally, his recompense is Hell' was revealed and we became worried about it. Then the Verse in Al-Furqan 'And those who invoke not any other ilah (god) along with Allah, or kill such person as Allah has forbidden, except by right.' was revealed."
أَنَّهُ قَالَ نَزَلَتْ { وَمَنْ يَقْتُلْ مُؤْمِنًا مُتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ خَالِدًا فِيهَا } أَشْفَقْنَا مِنْهَا فَنَزَلَتِ الآيَةُ الَّتِي فِي الْفُرْقَانِ { وَالَّذِينَ لاَ يَدْعُونَ مَعَ اللَّهِ إِلَهًا آخَرَ وَلاَ يَقْتُلُونَ النَّفْسَ الَّتِي حَرَّمَ اللَّهُ إِلاَّ بِالْحَقِّ }