"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." (Using translation from Nasāʾī 4008)
نَزَلَتْ {وَمَنْ يُقْتَلْ مُؤْمِنًا مُتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ خَالِدًا فِيهَا} [النساء 93] أَشْفَقْنَا مِنْهَا فَنَزَلَتِ الْآيَةُ الَّتِي فِي الْفُرْقَانِ {وَالَّذِينَ لَا يَدْعُونَ مَعَ اللهِ إِلَهًا آخَرَ وَلَا يَقْتُلُونَ النَّفْسَ الَّتِي حَرَّمَ اللهُ إِلَّا بِالْحَقِّ} [الفرقان 68]